Prevent sole admin from deleting their account

Without this guard, the last admin in the system could delete their own
account, making the application unmanageable. This adds a model method
`User#sole_admin?`, a controller guard in `RegistrationsController#destroy`,
and disables the delete button in the profile edit view when the current
user is the only remaining admin.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

DESIGN.md

@@ -1,34 +0,0 @@
-DESIGN
-======
-
-Below is a list of design decisions. The justification is to be consulted
-whenever a change is considered, to avoid regressions.
-
-### Data type for DB storage of numeric values (`decimal` vs `float`)
-
-* among database engines supported (by Rails), SQLite offers storage of
-  `decimal` data type with the lowest precision, equal to the precision of
-  `REAL` type (double precision float value, IEEE 754), but in a floating point
-  format,
-    * decimal types in other database engines offer greater precision, but store
-      data in a fixed point format,
-* biology-related values differ by several orders of magnitude; storing them in
-  fixed point format would only make sense if required precision would be
-  greater than that offered by floating point format,
-    * even then, fixed point would mean either bigger memory requirements or
-      worse precision for numbers close to scale limit,
-        * for a fixed point format to use the same 8 bytes of storage as IEEE
-          754, precision would need to be limited to 18 digits (4 bytes/9 digits)
-          and scale approximately half of that - 9,
-    * double precision floating point guarantees 15 digits of precision, which
-      is more than enough for all expected use cases,
-        * single precision floating point only guarntees 6 digits of precision,
-          which is estimated to be too low for some use cases (e.g. storing
-          latitude/longitude with a resolution grater than 100m)
-* double precision floating point (IEEE 754) is a standard that ensures
-  compatibility with all database engines,
-    * the same data format is used internally by Ruby as a `Float`; it
-      guarantees no conversions between storage and computation,
-    * as a standard with hardware implementations ensures both: computing
-      efficiency and hardware/3rd party library compatibility as opposed to Ruby
-      custom `BigDecimal` type

app/assets/images/pictograms/alert-outline.svg

@@ -1 +1 @@
-<svg xmlns="http://www.w3.org/2000/svg" id="icon" viewBox="0 0 24 24"><path d="M12,2L1,21H23M12,6L19.53,19H4.47M11,10V14H13V10M11,16V18H13V16" /></svg>
+<svg xmlns="http://www.w3.org/2000/svg" id="icon" viewBox="0 0 24 24"><path fill="#ffffff" d="M12,2L1,21H23M12,6L19.53,19H4.47M11,10V14H13V10M11,16V18H13V16" /></svg>

app/assets/images/pictograms/check-circle-outline.svg

@@ -1 +1 @@
-<svg xmlns="http://www.w3.org/2000/svg" id="icon" viewBox="0 0 24 24"><path d="M12 2C6.5 2 2 6.5 2 12S6.5 22 12 22 22 17.5 22 12 17.5 2 12 2M12 20C7.59 20 4 16.41 4 12S7.59 4 12 4 20 7.59 20 12 16.41 20 12 20M16.59 7.58L10 14.17L7.41 11.59L6 13L10 17L18 9L16.59 7.58Z" /></svg>
+<svg xmlns="http://www.w3.org/2000/svg" id="icon" viewBox="0 0 24 24"><path fill="#ffffff" d="M12 2C6.5 2 2 6.5 2 12S6.5 22 12 22 22 17.5 22 12 17.5 2 12 2M12 20C7.59 20 4 16.41 4 12S7.59 4 12 4 20 7.59 20 12 16.41 20 12 20M16.59 7.58L10 14.17L7.41 11.59L6 13L10 17L18 9L16.59 7.58Z" /></svg>

app/assets/stylesheets/application.css

@@ -18,12 +18,10 @@
 /* Strive for simplicity:
  * * style elements/tags only - if possible,
  * * replace element/tag name with class name - if element has to be styled
- * differently depending on context (e.g. <form>, <table>, <a> as link/button),
+ * differently depending on context (e.g. form)
- * * styles with multiple selectors should have all selectors with same
- * specificity, to allow proper rule specificity vs order management.
  *
- * NOTE: style in a modular way, similar to how CSS @scope would be used,
+ * NOTE: Style in a modular way, similar to how CSS @scope would be used,
- * to make transition easier once @scope is widely available. */
+ * to make transition easier once @scope is widely available */
 :root {
   --color-focus-gray: #f3f3f3;
   --color-border-gray: #dddddd;
@@ -55,36 +53,17 @@
 :focus-visible {
   outline: none;
 }
-/* NOTE: move to higher priority layer instead of using !important?; add CSS
- * @layer requirements in README */
-[disabled] {
-  border-color: var(--color-border-gray) !important;
-  color: var(--color-border-gray) !important;
-  /* NOTE: cannot set cursor when `pointer-events: none`; can be fixed by setting
-   * `cursor` on wrapping element.
-  cursor: not-allowed; */
-  fill: var(--color-border-gray) !important;
-  pointer-events: none !important;
-}
-/* Styles set `display` without distinguishing between [hidden] elements, making
- * them visible. */
-[hidden] {
-  display: none !important;
-}
 
 
 /* Color coding of input controls' background:
- *  blue - target for interaction with pointer,
+ *  blue - target for interaction with pointer
- *  gray - target for interaction with keyboard,
+ *  gray - target for interaction with keyboard
- *  red - destructive, non-undoable action.
+ *  red - destructive, non-undoable action
  */
-/* TODO: merge selectors using :is() */
-a,
 button,
 details,
 input,
 select,
-summary,
 textarea {
   background-color: inherit;
   font: inherit;
@@ -94,24 +73,56 @@ input,
 select {
   text-align: inherit;
 }
+a,
+button,
+input[type=submit] {
+  cursor: pointer;
+  text-decoration: none;
+  white-space: nowrap;
+}
+/* [hidden] submit controls cannot have `display` set as it makes them visible */
+.button,
+button:not([hidden]),
+input[type=submit]:not([hidden]),
+.tab {
+  align-items: center;
+  color: var(--color-gray);
+  display: flex;
+  fill: var(--color-gray);
+  font-weight: bold;
+}
+.button,
+button,
+input[type=submit] {
+  font-size: 0.8rem;
+  padding: 0.6em 0.5em;
+  width: fit-content;
+}
+input:not([type=submit]):not([type=checkbox]),
+select,
+summary,
+textarea {
+  padding: 0.2em 0.4em;
+}
+.button,
+button,
 input,
 select,
 summary,
 textarea {
-  border: 1px solid var(--color-gray);
+  border: solid 1px var(--color-gray);
   border-radius: 0.25em;
-  padding: 0.2em 0.4em;
 }
-svg {
+[name=cancel],
-  height: 1.4em;
+.auxiliary {
-  margin: 0 0.2em 0 0;
+  border-color: var(--color-border-gray);
-  width: 1.4em;
+  color: var(--color-nav-gray);
-}
+  fill: var(--color-nav-gray);
-svg:last-child {
-  margin-right: 0;
 }
+input[type=checkbox],
+svg,
 textarea {
-  margin: 0;
+  margin: 0
 }
 input[type=checkbox] {
   accent-color: var(--color-blue);
@@ -119,20 +130,17 @@ input[type=checkbox] {
   -webkit-appearance: none;
   display: flex;
   height: 1.1em;
-  margin: 0;
-  padding: 0;
   width: 1.1em;
 }
 input[type=checkbox]:checked {
   appearance: checkbox;
   -webkit-appearance: checkbox;
 }
-/* Hide spin buttons of <input type=number>. */
+/* Hide spin buttons in input number fields */
-/* TODO: add spin buttons inside <input type=number>: before (-) and after (+) input. */
+/* TODO: add spin buttons inside input[number]: before (-) and after (+) input */
 input[type=number] {
   appearance: textfield;
   -moz-appearance: textfield;
-  text-align: end;
 }
 input::-webkit-inner-spin-button {
   -webkit-appearance: none;
@@ -141,108 +149,37 @@ input::-webkit-outer-spin-button {
   -webkit-appearance: none;
   margin: 0;
 }
-/* Text color of table form controls:
+.button > svg,
- *  - black for row/table forms,
+.tab > svg,
- *  - inherited for internal (column specific) buttons/forms. */
+button > svg {
-table input,
+  height: 1.4em;
-table select,
+  width: 1.4em;
-table summary,
-table textarea {
-  border-color: var(--color-border-gray);
 }
-table input,
+.button > svg:not(:last-child),
-table select,
+.tab > svg:not(:last-child),
-table textarea {
+button > svg:not(:last-child) {
-  padding-block: 0.375em;
+  margin-right: 0.2em;
 }
-table form input,
+/* TODO: move normal non-button links (<a>:hover/:focus) styling here (i.e.
-table form select,
+ * page-wide, top-level) and remove from table.items - as the style should be
-table form summary,
+ * same everywhere */
-table form textarea {
+.button:focus-visible,
-  color: inherit;
+button:focus-visible,
-}
+input[type=submit]:focus-visible {
-table svg:not(:only-child) {
+  background-color: var(--color-focus-gray);
-  height: 1.25em;
-  width: 1.25em;
 }
 input:focus-visible,
 select:focus-visible,
 select:focus-within,
-/* TODO: how to achieve `summary:focus-within` for `::details-content`? */
+/* TODO: how to achieve summary:focus-within for ::details-content? */
 summary:focus-visible,
 textarea:focus-visible {
   accent-color: var(--color-dark-blue);
   background-color: var(--color-focus-gray);
-  color: black;
 }
-input:hover,
+.button:hover,
-select:hover,
+button:hover,
-summary:hover,
+input[type=submit]:hover {
-textarea:hover {
-  border-color: var(--color-blue);
-  outline: 1px solid var(--color-blue);
-}
-select:hover,
-summary:hover {
-  color: black;
-  cursor: pointer;
-}
-/* TODO: style <details>/<summary> focus to match <select> as much as possible.
-summary:focus-visible::before,
-summary:hover::before {
-  background-color: black;
-}
- */
-input:invalid,
-select:invalid,
-textarea:invalid {
-  border-color: var(--color-red);
-  outline-color: var(--color-red);
-}
-
-/* `.button`: button-styled <a>, <button>, <input type=submit>.
- * `.link`: any other <a>.
- * `.tab`: tab-styled <a>.
- */
-.button,
-.link,
-.tab {
-  cursor: pointer;
-  text-decoration: none;
-  white-space: nowrap;
-}
-.button,
-.tab {
-  align-items: center;
-  color: var(--color-gray);
-  display: flex;
-  fill: var(--color-gray);
-  font-weight: bold;
-}
-.button {
-  border: 1px solid var(--color-gray);
-  border-radius: 0.25em;
-  font-size: 0.8rem;
-  padding: 0.6em 0.5em;
-  width: fit-content;
-}
-.link {
-  color: inherit;
-  text-decoration: underline 1px var(--color-border-gray);
-  text-underline-offset: 0.25em;
-}
-[name=cancel],
-.auxiliary {
-  border-color: var(--color-border-gray);
-  color: var(--color-nav-gray);
-  fill: var(--color-nav-gray);
-}
-.button:focus-visible,
-.tab:focus-visible,
-.tab:hover {
-  background-color: var(--color-focus-gray);
-}
-.button:hover {
   background-color: var(--color-blue);
   border-color: var(--color-blue);
   color: white;
@@ -252,24 +189,32 @@ textarea:invalid {
   background-color: var(--color-red);
   border-color: var(--color-red);
 }
-.link:focus-visible {
+input:hover,
-  text-decoration-color: var(--color-gray);
+select:hover,
+summary:hover,
+textarea:hover {
+  border-color: var(--color-blue);
+  outline: solid 1px var(--color-blue);
 }
-.link:hover {
+select:hover,
-  color: var(--color-blue);
+summary:hover {
-  text-decoration-color: var(--color-blue);
+  cursor: pointer;
 }
-table .button {
+input:invalid,
-  border-color: var(--color-border-gray);
+select:invalid,
-  color: var(--color-table-gray);
+textarea:invalid {
-  font-weight: normal;
+  border-color: var(--color-red);
-  height: 100%;
+  outline: solid 1px var(--color-red);
-  padding: 0.4em;
+}
+input[type=text]:read-only,
+textarea:read-only {
+  border: none;
+  padding-inline: 0;
 }
 
 
-/* NOTE: collapse gaps around empty rows (`topside`) once possible with
+/* NOTE: collapse gaps around empty rows (`topside`) once possible
- * `grid-collapse` property and remove alternative `grid-template-areas`.
+ * with grid-collapse property and remove alternative grid-template
  * https://github.com/w3c/csswg-drafts/issues/5813 */
 body {
   display: grid;
@@ -277,16 +222,16 @@ body {
   grid-template-areas:
     "header    header  header"
     "nav       nav     nav"
+    "leftside  topside rightside"
     "leftside  main    rightside";
   grid-template-columns: 1fr minmax(max-content, 2fr) 1fr;
   font-family: system-ui;
   margin: 0.4em;
 }
-body:has(> .topside-area) {
+body:not(:has(.topside-area)) {
   grid-template-areas:
     "header    header  header"
     "nav       nav     nav"
-    "leftside  topside rightside"
     "leftside  main    rightside";
 }
 
@@ -302,14 +247,18 @@ header {
   margin-inline-start: 4%;
 }
 .navigation > .tab {
-  border-bottom: 2px solid var(--color-nav-gray);
+  border-bottom: solid 2px var(--color-nav-gray);
   flex: 1;
   font-size: 1rem;
   justify-content: center;
   padding-block: 0.4em;
 }
+.navigation > .tab:hover,
+.navigation > .tab:focus-visible {
+  background-color: var(--color-focus-gray);
+}
 .navigation > .tab.active {
-  border-bottom: 4px solid var(--color-blue);
+  border-bottom: solid 4px var(--color-blue);
   color: var(--color-blue);
   fill: var(--color-blue);
 }
@@ -341,7 +290,7 @@ header {
 
 #flashes {
   display: grid;
-  row-gap: 0.4em;
+  gap: 0.2em;
   grid-template-columns: 1fr auto auto auto 1fr;
   left: 0;
   pointer-events: none;
@@ -357,17 +306,13 @@ header {
   display: grid;
   grid-column: 2/5;
   grid-template-columns: subgrid;
-  line-height: 2.2em;
   pointer-events: auto;
 }
-.flash:before {
-  filter: invert();
-  height: 1.4em;
-  margin: 0 0.5em;
-  width: 1.4em;
-}
 .flash.alert:before {
   content: url('pictograms/alert-outline.svg');
+  height: 1.4em;
+  margin: 0 0.5em;
+  width: 1.4em;
 }
 .flash.alert {
   border-color: var(--color-red);
@@ -375,24 +320,35 @@ header {
 }
 .flash.notice:before {
   content: url('pictograms/check-circle-outline.svg');
+  height: 1.4em;
+  margin: 0 0.5em;
+  width: 1.4em;
 }
 .flash.notice {
   border-color: var(--color-blue);
   background-color: var(--color-blue);
 }
-.flash svg {
+.flash > div {
-  cursor: pointer;
+  grid-column: 2;
-  fill: white;
-  height: 2.2em;
-  opacity: 0.6;
-  padding: 0.4em 0.5em;
-  width: 2.4em;
 }
-.flash svg:hover {
+/* NOTE: currently flash button inherits some unnecessary styles from generic
+ * button. */
+.flash > button {
+  border: none;
+  color: inherit;
+  cursor: pointer;
+  font-size: 1.4em;
+  font-weight: bold;
+  grid-column: 3;
+  opacity: 0.6;
+  padding: 0.2em 0.4em;
+}
+.flash > button:hover {
   opacity: 1;
 }
 
 
+/* TODO: Hover over invalid should work like in measurements (thin vs thick border) */
 .labeled-form {
   align-items: center;
   display: grid;
@@ -409,7 +365,7 @@ header {
 .labeled-form label.required {
   font-weight: bold;
 }
-/* Don't style `label.error + input` if case already covered by `input:invalid`. */
+/* Don't style `label.error + input` if case already covered by input:invalid */
 .labeled-form label.error {
   color: var(--color-red);
 }
@@ -429,117 +385,200 @@ header {
 .labeled-form .auxiliary {
   grid-column: 3;
   /* If more buttons are needed, `grid-row` can be replaced with
-   * `reading-flow: grid-columns` to ensure proper [tabindex] order. */
+   * `reading-flow: grid-columns` to ensure proper tabindex order */
   grid-row: 1;
   height: 100%;
   padding-block: 0;
 }
 
-.tabular-form table {
-  border: none;
-  border-spacing: 0.4em 0;
-  margin-inline: -0.4em;
-}
-.tabular-form table td {
-  border: none;
-  vertical-align: middle;
-}
-.tabular-form table td {
-  padding-inline: 0;
-}
-.tabular-form table :is(form, input, select, textarea):only-child {
-  margin-inline-start: 0;
-}
 
-
+/* TODO: remove .items class (?) and make 'form table' work properly */
-.items-table {
+table.items {
   border-spacing: 0;
-  border: 1px solid var(--color-border-gray);
+  border: solid 1px var(--color-border-gray);
   border-radius: 0.25em;
   font-size: 0.85rem;
   text-align: left;
 }
-.items-table thead {
+table:not(:has(tr)) {
+  display: none;
+}
+table.items thead {
   font-size: 0.8rem;
 }
-.items-table thead,
+table.items thead,
-.items-table tbody tr:hover {
+table.items tbody tr:hover {
   background-color: var(--color-focus-gray);
 }
-.items-table th {
+table.items th {
-  padding: 0.75em 0 0.75em 1em;
+  padding-block: 0.75em;
   text-align: center;
 }
-.items-table th:last-child {
+table.items th,
-  padding-inline-end: 0.4em;
+table.items td {
+  padding-inline: 1em 0;
 }
-.items-table td {
+/* For <a> to fill <td> completely, we use an ::after pseudoelement. */
-  border-top: 1px solid var(--color-border-gray);
+table.items td.link {
-  height: 2.4em;
+  padding: 0;
-  padding: 0.1em 0 0.1em calc(1em + var(--depth) * 0.8em);
-}
-.items-table td:last-child {
-  padding-inline-end: 0.1em;
-}
-.items-table :is(form, input, select, textarea):only-child {
-  margin-inline-start: calc(-0.4em - 0.9px);
-}
-/* For <a> to fill table cell completely, we use an `::after` pseudoelement. */
-/* TODO: expand to whole row? will require adjusting z-index on inputs/buttons */
-.items-table td:has(> .link) {
   position: relative;
 }
-.items-table .link::after {
+table.items td.link a {
+  color: inherit;
+  font: inherit;
+}
+table.items td.link a::after {
   content: '';
-  inset: -1px 0 0 0;
+  inset: 0;
   position: absolute;
 }
-.items-table .flex {
+table.items td:first-child {
+  padding-inline-start: calc(1em + var(--depth) * 0.8em);
+}
+table.items td:has(input, select, textarea) {
+  padding-inline-start: calc(0.6em - 0.9px);
+}
+table.items td:first-child:has(input, select, textarea) {
+  padding-inline-start: calc(0.6em + var(--depth) * 0.8em - 0.9px);
+}
+table.items th:last-child {
+  padding-inline-end: 0.4em;
+}
+table.items td:last-child {
+  padding-inline-end: 0.1em;
+}
+table.items td {
+  border-top: solid 1px var(--color-border-gray);
+  height: 2.4em;
+  padding-block: 0.1em;
+}
+table.items .actions {
+  display: flex;
   gap: 0.4em;
   justify-content: end;
 }
-.items-table .dropzone {
+table.items .actions.centered {
+  justify-content: center;
+}
+table.items tr.dropzone {
   position: relative;
 }
-.items-table .dropzone::after {
+table.items tr.dropzone::after {
   content: '';
   inset: 1px 0 0 0;
   position: absolute;
-  outline: 2px dashed var(--color-blue);
+  outline: dashed 2px var(--color-blue);
   outline-offset: -1px;
   z-index: var(--z-index-table-row-outline);
 }
-.items-table .handle {
+table.items td.handle {
-  cursor: grab;
+  cursor: move;
 }
-.items-table .form td {
+table.items tr.form td {
   vertical-align: top;
 }
-.items-table td:not(:first-child),
+
+/* TODO: replace :hover:focus-visible combos with proper LOVE stye order */
+/* TODO: Update table styling: simplify selectors, deduplicate, remove non-font rem. */
+table.items td.link a:hover,
+table.items td.link a:focus-visible,
+table.items td.link a:hover:focus-visible {
+  text-decoration: underline;
+  text-decoration-thickness: 0.05rem;
+  text-underline-offset: 0.2rem;
+}
+table.items td.link a:hover {
+  color: var(--color-blue);
+}
+table.items td.link a:focus-visible {
+  text-decoration-color: var(--color-gray);
+}
+table.items td.link a:hover:focus-visible {
+  color: var(--color-dark-blue);
+}
+
+table.items td:not(:first-child),
 .grayed {
   color: var(--color-table-gray);
-  fill: var(--color-gray);
+  fill: var(--color-table-gray);
 }
-.items-table td:has(> svg:only-child) {
+table.items svg {
+  height: 1rem;
+  vertical-align: middle;
+  width: 1rem;
+}
+table.items svg:last-child {
+  height: 1.2rem;
+  width: 1.2rem;
+}
+table.items td.svg {
   text-align: center;
 }
+table.items td.number {
+  text-align: right;
+}
+table.items .button,
+table.items button,
+table.items input[type=submit] {
+  font-weight: normal;
+  height: 100%;
+  padding: 0.4em;
+}
+table.items input:not([type=submit]):not([type=checkbox]),
+table.items select,
+table.items textarea {
+  padding-block: 0.375em;
+}
+/* TODO: find a way (layers?) to style inputs differently while making sure
+ * hover works properly without using :not(:hover) selectors here. */
+table.items .button:not(:hover),
+table.items button:not(:hover),
+table.items input:not(:hover),
+table.items select:not(:hover),
+table.items textarea:not(:hover) {
+  border-color: var(--color-border-gray);
+}
+table.items .button:not(:hover),
+table.items button:not(:hover),
+table.items input[type=submit]:not(:hover),
+table.items select:not(:hover) {
+  color: var(--color-table-gray);
+}
+table.items select:focus-within,
+table.items select:focus-visible {
+  color: black;
+}
+form table.items {
+  border: none;
+}
+form table.items td {
+  border: none;
+  text-align: left;
+  vertical-align: middle;
+}
+form table.items td:first-child {
+  color: inherit;
+}
 
 
-.center {
+.centered {
   margin: 0 auto;
 }
+.extendedright {
+  margin-right: auto;
+}
 .hexpand {
   width: 100%;
 }
-.flex {
+.hflex {
   display: flex;
   gap: 0.8em;
 }
-.flex.reverse {
+.hflex.reverse {
   flex-direction: row-reverse;
 }
-.flex.vertical {
+.hflex.centered {
-  flex-direction: column;
+  justify-content: center;
 }
 .hint {
   color: var(--color-table-gray);
@@ -547,18 +586,21 @@ header {
   font-size: 0.9rem;
   text-align: center;
 }
-.hmin50 {
+.vflex {
-  min-width: 50%;
+  display: flex;
+  gap: 0.8em;
+  flex-direction: column;
 }
-.italic {
+[disabled] {
-  color: var(--color-gray);
+/* label:has(input[disabled]) {
-  font-style: italic;
+ * TODO: disabled checkbox blue square focus removal; disabled label styling;
-}
+ * focused label styling (currently only checkbox has focus)
-.ralign {
+ * */
-  text-align: right;
+  border-color: var(--color-border-gray) !important;
-}
+  color: var(--color-border-gray) !important;
-.rextend {
+  cursor: not-allowed;
-  margin-right: auto;
+  fill: var(--color-border-gray) !important;
+  pointer-events: none;
 }
 
 
@@ -570,12 +612,12 @@ summary {
   align-items: center;
   color: var(--color-gray);
   display: flex;
-  gap: 0.4em;
+  gap: 0.2em;
   height: 100%;
   white-space: nowrap;
 }
 summary::before {
-  background-color: currentColor;
+  background-color: #000;
   content: "";
   height: 1em;
   mask-image: url('pictograms/chevron-down.svg');
@@ -587,7 +629,7 @@ summary:has(.button) {
   padding-inline-end: 0;
 }
 summary .button {
-  border: 1px solid var(--color-border-gray);
+  border: solid 1px var(--color-border-gray);
   border-radius: inherit;
   border-top-left-radius: 0;
   border-bottom-left-radius: 0;
@@ -598,15 +640,15 @@ summary span {
   width: 100%;
 }
 details[open] summary::before {
-  transform: scaleY(-1);
+  transform: rotate(180deg);
 }
 summary::marker {
   padding-left: 0.25em;
 }
-/* NOTE: use `details[open]::details-content` once widely available. */
+/* NOTE: use details[open]::details-content once widely available */
 details[open] ul {
-  background-color: white;
+  background: white;
-  border: 1px solid var(--color-border-gray);
+  border: solid 1px var(--color-border-gray);
   border-radius: 0.25em;
   box-shadow: 1px 1px 3px var(--color-border-gray);
   margin: -1px 0 0 0;
@@ -628,15 +670,3 @@ li input[type=checkbox] {
 li::marker {
   content: '';
 }
-/*
- * TODO:
- * * disable <label> containing disabled checkbox: `label:has(input[disabled])`,
- * * disabled label styling,
- * * focused label styling (currently only checkbox has focus),
- * * disabled checkbox blue square focus removal.
- * */
-
-#measurement_form {
-  min-width: 66%;
-  width: max-content;
-}

app/controllers/user/profiles_controller.rb

@@ -1,6 +1,10 @@
 class User::ProfilesController < Devise::RegistrationsController
   def destroy
-    # TODO: Disallow/disable deletion for last admin account; update :edit view
+    if current_user.sole_admin?
+      redirect_back fallback_location: edit_user_registration_path,
+        alert: t(".sole_admin")
+      return
+    end
     super
   end
 

app/helpers/application_helper.rb

@@ -12,12 +12,6 @@ module ApplicationHelper
       labeled_field_for(method, options) { super }
     end
 
-    def submit(value = nil, options = {})
-      value, options = nil, value if value.is_a?(Hash)
-      options[:class] = @template.class_names('button', options[:class])
-      super
-    end
-
     private
 
     def labeled_field_for(method, options)
@@ -102,28 +96,20 @@ module ApplicationHelper
 
     def number_field(method, options = {})
       attr_type = object.type_for_attribute(method)
-      case attr_type.type
+      if attr_type.type == :decimal
-      when :decimal
         options[:value] = object.public_send(method)&.to_scientific
         options[:step] ||= BigDecimal(10).power(-attr_type.scale)
         options[:max] ||= BigDecimal(10).power(attr_type.precision - attr_type.scale) -
           options[:step]
         options[:min] = options[:min] == :step ? options[:step] : options[:min]
         options[:min] ||= -options[:max]
-        options[:size] ||= attr_type.precision / 2
-      when :float
-        options[:size] ||= 6
       end
       super
     end
 
     def button(value = nil, options = {}, &block)
-      # #button does not use #objectify_options/@default_options
+      # button does not use #objectify_options
-      value, options = nil, value if value.is_a?(Hash)
+      options.merge!(@options.slice(:form))
-      options = options.merge(
-        @default_options.slice(:form),
-        class: @template.class_names('button', options[:class])
-      )
       super
     end
 
@@ -152,14 +138,12 @@ module ApplicationHelper
   end
 
   def tabular_form_with(**options, &block)
-    extra_options = {builder: TabularFormBuilder, class: 'tabular-form',
+    extra_options = {builder: TabularFormBuilder, html: {autocomplete: 'off'}}
-                     html: {autocomplete: 'off'}}
     form_with(**merge_attributes(options, extra_options), &block)
   end
 
   def svg_tag(source, label = nil, options = {})
-    label, options = nil, label if label.is_a? Hash
+    svg_tag = tag.svg(options) do
-    svg_tag = tag.svg(**options) do
       tag.use(href: "#{image_path(source + ".svg")}#icon")
     end
     label.blank? ? svg_tag : svg_tag + tag.span(label)
@@ -228,8 +212,9 @@ module ApplicationHelper
       # Conversion of flash to Array only required because of Devise
       Array(messages).map do |message|
         tag.div class: "flash #{entry}" do
-          tag.span(sanitize(message)) +
+          # TODO: change button text to svg to make it aligned vertically
-            svg_tag('pictograms/close-outline', {onclick: "this.parentElement.remove()"})
+          tag.div(sanitize(message)) + tag.button(sanitize("×"), tabindex: -1,
+                                                  onclick: "this.parentElement.remove();")
         end
       end
     end.join.html_safe

app/helpers/quantities_helper.rb

@@ -1,9 +1,9 @@
 module QuantitiesHelper
-  def quantities_check_boxes(quantities)
+  def quantities_check_boxes
     # Closing <details> on focusout event depends on relatedTarget for internal
     # actions being non-null. To ensure this, all top-layer elements of
     # ::details-content must accept focus, e.g. <label> needs tabindex="-1" */
-    collection_check_boxes(nil, :quantity, quantities, :id, :to_s_with_depth,
+    collection_check_boxes(nil, :quantity, @quantities, :id, :to_s_with_depth,
                            include_hidden: false) do |b|
       content_tag :li, b.label(tabindex: -1) { b.check_box + b.text }
     end

app/models/user.rb

@@ -29,4 +29,11 @@ class User < ApplicationRecord
   def at_least(status)
     User.statuses[self.status] >= User.statuses[status]
   end
+
+  # Returns true when this user is the only admin account in the system.
+  # Used to block actions that would leave the application without an admin
+  # (account deletion, status demotion).
+  def sole_admin?
+    admin? && !User.admin.where.not(id: id).exists?
+  end
 end

app/views/default/units/_unit.html.erb

@@ -5,7 +5,7 @@
   </td>
 
   <% if current_user.at_least(:active) %>
-    <td class="flex">
+    <td class="actions">
       <% unless unit.portable.nil? %>
         <% if unit.default? %>
           <%= image_button_to_if unit.portable?, t('.import'), 'download-outline',

app/views/default/units/index.html.erb

@@ -8,7 +8,7 @@
     class: 'tools-area' %>
 </div>
 
-<table class="main-area items-table">
+<table class="main-area items">
   <thead>
     <tr>
       <th><%= Unit.human_attribute_name(:symbol) %></th>

app/views/layouts/application.html.erb

@@ -23,10 +23,10 @@
   </head>
 
   <body>
-    <header class="flex">
+    <header class="hflex">
       <%= image_link_to t(".source_code"), "code-braces", source_code_url %>
       <%= image_link_to t(".issue_tracker"), "bug-outline", issue_tracker_url,
-        class: "rextend" %>
+            class: "extendedright" %>
       <% if user_signed_in? %>
         <%= image_link_to_unless_current(current_user, "account-wrench-outline",
           edit_user_registration_path) %>

app/views/measurements/_form.html.erb

@@ -1,37 +1,28 @@
 <%= tabular_form_with model: Measurement.new, id: :measurement_form,
-  class: 'topside-area flex vertical center',
+  class: 'topside-area vflex', html: {onkeydown: 'formProcessKey(event)'} do |form| %>
-  html: {onkeydown: 'formProcessKey(event)'} do |form| %>
+  <table class="items centered">
-
+    <tbody id="readouts"></tbody>
-  <table class="items-table center">
-    <tbody id="readouts">
-      <%= tabular_fields_for @measurement do |form| %>
-        <tr class="italic">
-          <td class="hexpand hmin50"><%= t '.taken_at_html' %></td>
-          <td colspan="3" class="ralign">
-            <%= form.datetime_field :taken_at, required: true %>
-          </td>
-        </tr>
-      <% end %>
-    </tbody>
   </table>
 
-  <%# TODO: right-click selection; unnecessary with hierarchical tags? %>
+  <div class="hflex">
-  <details id="quantity_select" class="center hexpand" open
+    <%# TODO: right-click selection %>
-           onkeydown="detailsProcessKey(event)">
+    <details id="quantity_select" class="hexpand" open
-    <summary autofocus>
+             onkeydown="detailsProcessKey(event)">
-      <!-- TODO: Set content with CSS when span empty to avoid duplication -->
+      <summary autofocus>
-      <span data-prompt="<%= t('.select_quantity') %>">
+        <!-- TODO: Set content with CSS when span empty to avoid duplication -->
-        <%= t('.select_quantity') %>
+        <span data-prompt="<%= t('.select_quantity') %>">
-      </span>
+          <%= t('.select_quantity') %>
-      <%= image_button_tag t(:apply), "update", name: nil, disabled: true,
+        </span>
-        formaction: new_readout_path, formmethod: :get, formnovalidate: true,
+        <%= image_button_tag t(:apply), "update", name: nil, disabled: true,
-        data: {turbo_stream: true} %>
+          formaction: new_readout_path, formmethod: :get, formnovalidate: true,
-    </summary>
+          data: {turbo_stream: true} %>
-    <ul><%= quantities_check_boxes(@quantities) %></ul>
+      </summary>
-  </details>
+      <ul><%= quantities_check_boxes %></ul>
-
+    </details>
-  <div class="flex reverse">
     <%= form.button id: :create_measurement_button, disabled: true -%>
+  </div>
+
+  <div class="hflex reverse">
     <%= image_link_to t(:cancel), "close-outline", measurements_path, name: :cancel,
       class: 'dangerous', onclick: render_turbo_stream('form_close') %>
   </div>

app/views/quantities/_form.html.erb

@@ -9,7 +9,7 @@
       <%= form.text_area :description, cols: 30, rows: 1, escape: false %>
     </td>
 
-    <td class="flex">
+    <td class="actions">
       <%= form.button %>
       <%= image_link_to t(:cancel), "close-outline", quantities_path, class: 'dangerous',
         name: :cancel, onclick: render_turbo_stream('form_close', {row: row}) %>

app/views/quantities/_quantity.html.erb

@@ -5,14 +5,14 @@
            data: {drag_path: reparent_quantity_path(quantity), drop_id: dom_id(quantity),
                   drop_id_param: "quantity[parent_id]"} do %>
 
-  <td style="--depth:<%= quantity.depth %>">
+  <td class="link" style="--depth:<%= quantity.depth %>">
-    <%= link_to quantity, edit_quantity_path(quantity), class: 'link',
+    <%= link_to quantity, edit_quantity_path(quantity), onclick: 'this.blur();',
-      onclick: 'this.blur();', data: {turbo_stream: true} %>
+      data: {turbo_stream: true} %>
   </td>
   <td><%= quantity.description %></td>
 
   <% if current_user.at_least(:active) %>
-    <td class="flex">
+    <td class="actions">
       <%= image_link_to t('.new_subquantity'), 'plus-outline', new_quantity_path(quantity),
         id: dom_id(quantity, :new, :link), onclick: 'this.blur();', data: {turbo_stream: true} %>
 

app/views/quantities/index.html.erb

@@ -8,14 +8,13 @@
     class: 'tools-area' %>
 </div>
 
-<%# TODO: remove? form can be inserted directly, e.g. at the end of index %>
 <%= tag.div class: 'main-area', id: :quantity_form %>
 
-<table class="main-area items-table">
+<table class="main-area items">
   <thead>
     <tr>
       <th><%= Quantity.human_attribute_name(:name) %></th>
-      <th class="hexpand"><%= Quantity.human_attribute_name(:description) %></th>
+      <th><%= Quantity.human_attribute_name(:description) %></th>
       <% if current_user.at_least(:active) %>
         <th><%= t :actions %></th>
         <th></th>

app/views/readouts/_form.html.erb

@@ -1,24 +1,25 @@
 <%# TODO: add readout reordering by dragging %>
 <%= tabular_fields_for 'readouts[]', readout do |form| %>
   <%- tag.tr id: dom_id(readout.quantity, :new, :readout) do %>
-    <td>
+    <td class="actions">
-      <%# TODO: add grayed readout index (in separate column?) %>
-      <%= readout.quantity.relative_pathname(@superquantity) %>
-      <%= form.hidden_field :quantity_id %>
-    </td>
-    <td>
-      <%= form.number_field :value, required: true, autofocus: readout_counter == 0 %>
-    </td>
-    <td>
-      <%= form.collection_select :unit_id, @user_units, :id,
-        ->(u){ sanitize('&emsp;' * (u.base_id ? 1 : 0) + u.symbol) },
-        {prompt: '', disabled: '', selected: ''}, required: true %>
-    </td>
-    <td class="flex">
       <%# TODO: change to _link_ after giving up displaying relative paths %>
       <%= image_button_tag '', 'delete-outline', class: 'dangerous', name: nil,
         formaction: discard_readouts_path(readout.quantity),
         formmethod: :get, formnovalidate: true, data: {turbo_stream: true} %>
     </td>
+    <td>
+      <%= readout.quantity.relative_pathname(@superquantity) %>
+    </td>
+    <td>
+      <%= form.number_field :value, required: true,
+        size: readout.type_for_attribute(:value).precision / 2,
+        autofocus: readout_counter == 0 %>
+    </td>
+    <td>
+      <%= form.hidden_field :quantity_id %>
+      <%= form.collection_select :unit_id, @user_units, :id,
+        ->(u){ sanitize('&emsp;' * (u.base_id ? 1 : 0) + u.symbol) },
+        {prompt: t('.select_unit'), disabled: '', selected: ''}, required: true %>
+    </td>
   <% end %>
 <% end %>

app/views/units/_form.html.erb

@@ -8,11 +8,11 @@
     <td>
       <%= form.text_area :description, cols: 30, rows: 1, escape: false %>
     </td>
-    <td>
+    <td class="number">
       <%= form.number_field :multiplier, required: true, size: 10, min: :step if @unit.base_id? %>
     </td>
 
-    <td class="flex">
+    <td class="actions">
       <%= form.button %>
       <%= image_link_to t(:cancel), "close-outline", units_path, class: 'dangerous',
         name: :cancel, onclick: render_turbo_stream('form_close', {row: row}) %>

app/views/units/_unit.html.erb

@@ -6,15 +6,14 @@
                   drop_id: dom_id(unit.base || unit),
                   drop_id_param: "unit[base_id]"} do %>
 
-  <td style="--depth:<%= unit.base_id? ? 1 : 0 %>">
+  <td class="link" style="--depth:<%= unit.base_id? ? 1 : 0 %>">
-    <%= link_to unit, edit_unit_path(unit), class: 'link', onclick: 'this.blur();',
+    <%= link_to unit, edit_unit_path(unit), onclick: 'this.blur();', data: {turbo_stream: true} %>
-      data: {turbo_stream: true} %>
   </td>
   <td><%= unit.description %></td>
-  <td class="ralign"><%= unit.multiplier.to_html %></td>
+  <td class="number"><%= unit.multiplier.to_html %></td>
 
   <% if current_user.at_least(:active) %>
-    <td class="flex">
+    <td class="actions">
       <% unless unit.base_id? %>
         <%= image_link_to t('.new_subunit'), 'plus-outline', new_unit_path(unit),
           id: dom_id(unit, :new, :link), onclick: 'this.blur();', data: {turbo_stream: true} %>

app/views/units/index.html.erb

@@ -7,14 +7,13 @@
     class: 'tools-area' %>
 </div>
 
-<%# TODO: remove? form can be inserted directly, e.g. at the end of index %>
 <%= tag.div id: :unit_form %>
 
-<table class="main-area items-table">
+<table class="main-area items">
   <thead>
     <tr>
       <th><%= Unit.human_attribute_name(:symbol) %></th>
-      <th class="hexpand"><%= Unit.human_attribute_name(:description) %></th>
+      <th><%= Unit.human_attribute_name(:description) %></th>
       <th><%= Unit.human_attribute_name(:multiplier) %></th>
       <% if current_user.at_least(:active) %>
         <th><%= t :actions %></th>

app/views/users/index.html.erb

@@ -1,4 +1,4 @@
-<table class="main-area items-table" id="users">
+<table class="main-area items" id="users">
   <thead>
     <tr>
       <th><%= User.human_attribute_name(:email) %></th>
@@ -11,7 +11,7 @@
   <tbody>
     <% @users.each do |user| %>
       <tr>
-        <td><%= link_to user, user_path(user), class: 'link' %></td>
+        <td class="link"><%= link_to user, user_path(user) %></td>
         <td>
           <% if user == current_user %>
             <%= user.status %>
@@ -22,11 +22,11 @@
             <% end %>
           <% end %>
         </td>
-        <td>
+        <td class="svg">
           <%= svg_tag 'pictograms/checkbox-marked-outline' if user.confirmed_at.present? %>
         </td>
         <td><%= l user.created_at, format: :without_tz %></td>
-        <td class="flex">
+        <td class="actions">
           <% if allow_disguise?(user) %>
             <%= image_link_to t('.disguise'), 'incognito', disguise_user_path(user) %>
           <% end %>

app/views/users/profiles/edit.html.erb

@@ -4,9 +4,8 @@
 <% end %>
 
 <div class="rightside-area buttongrid">
-  <%#= TODO: Disallow/disable deletion for last admin account, image_button_to_if %>
+  <%= image_button_to_if !current_user.sole_admin?, t('.delete'), 'account-remove-outline',
-  <%= image_button_to t('.delete'), 'account-remove-outline', user_registration_path,
+    user_registration_path, form_class: 'tools-area', method: :delete, data: {turbo: false},
-    form_class: 'tools-area', method: :delete, data: {turbo: false},
     onclick: {confirm: t('.confirm_delete')} %>
 </div>
 

app/views/users/profiles/new.html.erb

@@ -10,6 +10,7 @@
 
   <%= f.submit t(:register), data: {turbo: false} %>
 
+  <%# TODO: fix button text color after change link -> button %>
   <%= image_button_tag t(:resend_confirmation), 'email-sync-outline',
     class: 'auxiliary', formaction: user_confirmation_path, formnovalidate: true,
     data: {validate: f.field_id(:email)} %>

app/views/users/unlocks/new.html.erb

@@ -8,7 +8,7 @@
     <%= f.email_field :email, autofocus: true, autocomplete: "email" %>
   </div>
 
-  <div class="flex">
+  <div class="actions">
     <%= f.submit "Resend unlock instructions" %>
   </div>
 <% end %>

config/application.rb.dist

@@ -20,10 +20,6 @@ Bundler.require(*Rails.groups)
 
 module FixinMe
   class Application < Rails::Application
-    # Allow RAILS_DATABASE_YML to override the database config file path.
-    # Used by `rails test:all_databases` to test against multiple DB adapters.
-    config.paths['config/database'] = [ENV['RAILS_DATABASE_YML']] if ENV['RAILS_DATABASE_YML']
-
     # Initialize configuration defaults for originally generated Rails version.
     config.load_defaults 7.0
 

config/database.yml.dist

@@ -48,26 +48,3 @@ production:
 #test:
 #  <<: *default
 #  database: fixinme_test
-
-# Multi-database testing — `bundle exec rails test:all_databases`
-# ---------------------------------------------------------------
-# Add any number of `test_<name>:` blocks to run the full test suite
-# against additional database adapters in a single command.
-# Each adapter's gem must be available in the bundle:
-#   bundle config --local with "mysql:sqlite"   # mysql + sqlite
-#   bundle config --local with "mysql:pg"       # mysql + postgresql
-#
-# Example — run tests against MySQL and SQLite:
-#
-#test_sqlite:
-#  adapter: sqlite3
-#  database: db/fixinme_test.sqlite3
-#
-# Example — run tests against MySQL and PostgreSQL:
-#
-#test_pg:
-#  adapter: postgresql
-#  database: fixinme_test
-#  username: fixinme
-#  password: Some-password1%
-#  host: localhost

config/locales/en.yml

@@ -85,10 +85,12 @@ en:
     navigation: Measurements
     no_items: There are no measurements taken. You can Add some now.
     form:
-      select_quantity: select quantities...
+      select_quantity: select the measured quantities...
-      taken_at_html: Measurement taken at 
     index:
       new_measurement: Add measurement
+  readouts:
+    form:
+      select_unit: ...
   quantities:
     navigation: Quantities
     no_items: There are no configured quantities. You can Add some or Import from defaults.
@@ -160,6 +162,9 @@ en:
           New password:
           <br><em>leave blank to keep unchanged</em>
           %{password_length_hint_html}
+  registrations:
+    destroy:
+      sole_admin: You cannot delete the only admin account.
   actions: Actions
   add: Add
   apply: Apply

db/migrate/20250121230456_create_readouts.rb

@@ -1,14 +1,10 @@
 class CreateReadouts < ActiveRecord::Migration[7.2]
   def change
     create_table :readouts do |t|
-      # Reference :user through :quantity (:measurement may be NULL).
+      t.references :user, null: false, foreign_key: true
-      t.references :measurement, foreign_key: true
       t.references :quantity, null: false, foreign_key: true
-      # :category + :value + :unit as a separate table? (NumericValue, TextValue)
-      t.integer :category, null: false, default: 0
-      t.float :value, null: false, limit: Float::MANT_DIG
       t.references :unit, foreign_key: true
-      # Move to Measurement?
+      t.decimal :value, null: false, precision: 30, scale: 15
       #t.references :collector, foreign_key: true
       #t.references :device, foreign_key: true
 

lib/tasks/test_databases.rake

@@ -1,118 +0,0 @@
-require 'yaml'
-require 'erb'
-require 'tmpdir'
-
-namespace :test do
-  desc <<~DESC
-    Run the full test suite against every test database configured in database.yml.
-
-    Any top-level key that starts with "test" and contains a Hash is treated as a
-    test database configuration:
-
-      test:           # always required — the primary test database
-        adapter: mysql2
-        database: fixinme_test
-        ...
-
-      test_sqlite:    # optional additional databases
-        adapter: sqlite3
-        database: db/fixinme_test.sqlite3
-
-      test_pg:
-        adapter: postgresql
-        database: fixinme_test
-        ...
-
-    For each database the task will:
-      1. Check that the required adapter gem is available (skip with warning if not).
-      2. Run `rails db:test:prepare` to create/migrate the database.
-      3. Run `rails test` and record pass/fail.
-
-    A summary is printed at the end. The task exits non-zero if any database fails.
-  DESC
-  task :all_databases do
-    db_file    = Rails.root.join('config', 'database.yml')
-    all        = YAML.safe_load(ERB.new(db_file.read).result, aliases: true) || {}
-    test_cfgs  = all.select { |k, v| k.to_s.start_with?('test') && v.is_a?(Hash) }
-    non_test   = all.reject { |k, _| k.to_s.start_with?('test') }
-
-    abort "No test database configurations found in #{db_file}." if test_cfgs.empty?
-
-    results = {}
-
-    test_cfgs.each do |name, config|
-      adapter = config['adapter'].to_s
-
-      puts "\n#{'─' * 64}"
-      puts "  #{name}  (adapter: #{adapter})"
-      puts '─' * 64
-
-      unless adapter_available?(adapter)
-        puts "  SKIPPED — gem for '#{adapter}' adapter not available in bundle."
-        puts "  Add it to Gemfile (e.g. `bundle config --local with #{adapter_group(adapter)}`)"
-        results[name] = :skipped
-        next
-      end
-
-      Dir.mktmpdir('rails_test_db_') do |tmpdir|
-        tmp_yml = File.join(tmpdir, 'database.yml')
-        # Write a standalone database.yml with just this config as `test:`
-        # (non-test configs are preserved so boot doesn't fail on `production:` lookup)
-        File.write(tmp_yml, non_test.merge('test' => config).to_yaml)
-
-        env = { 'RAILS_DATABASE_YML' => tmp_yml }
-
-        if system(env, 'bundle exec rails db:test:prepare')
-          results[name] = system(env, 'bundle exec rails test') ? :pass : :fail
-        else
-          results[name] = :prepare_failed
-        end
-      end
-    end
-
-    puts "\n#{'═' * 64}"
-    puts "  SUMMARY"
-    puts '═' * 64
-    results.each do |name, status|
-      adapter = test_cfgs[name]['adapter']
-      icon    = { pass: '✓', fail: '✗', prepare_failed: '✗', skipped: '–' }[status]
-      label   = { pass: 'PASS', fail: 'FAIL',
-                  prepare_failed: 'PREPARE FAILED', skipped: 'SKIPPED' }[status]
-      puts "  #{icon}  #{name.ljust(26)} (#{adapter.ljust(12)})  #{label}"
-    end
-    puts '═' * 64
-
-    failed = results.count { |_, s| s == :fail || s == :prepare_failed }
-    abort "\n  #{failed} database(s) failed." if failed > 0
-  end
-end
-
-private
-
-# Returns true if the gem required for this adapter is loadable.
-ADAPTER_GEMS = {
-  'mysql2'     => 'mysql2',
-  'sqlite3'    => 'sqlite3',
-  'postgresql' => 'pg',
-  'pg'         => 'pg',
-}.freeze
-
-def adapter_available?(adapter)
-  gem_name = ADAPTER_GEMS.fetch(adapter, adapter)
-  require gem_name
-  true
-rescue LoadError
-  false
-end
-
-# Returns the Bundler group name that installs the adapter gem.
-ADAPTER_GROUPS = {
-  'mysql2'     => 'mysql',
-  'sqlite3'    => 'sqlite',
-  'postgresql' => 'postgresql',
-  'pg'         => 'postgresql',
-}.freeze
-
-def adapter_group(adapter)
-  ADAPTER_GROUPS.fetch(adapter, adapter)
-end

test/controllers/registrations_controller_test.rb

@@ -0,0 +1,18 @@
+require "test_helper"
+
+class RegistrationsControllerTest < ActionDispatch::IntegrationTest
+  test "sole admin cannot delete account" do
+    sign_in users(:admin)
+    delete user_registration_path
+    assert_redirected_to edit_user_registration_path
+    assert_equal t("registrations.destroy.sole_admin"), flash[:alert]
+    assert User.exists?(users(:admin).id)
+  end
+
+  test "non-admin can delete account" do
+    sign_in users(:alice)
+    assert_difference ->{ User.count }, -1 do
+      delete user_registration_path
+    end
+  end
+end

test/system/users_test.rb

@@ -182,8 +182,8 @@ class UsersTest < ApplicationSystemTestCase
     assert_title 'Access is forbidden to this page (403)'
   end
 
-  test 'delete profile' do
+  test "delete profile" do
-    user = sign_in
+    user = sign_in user: users.reject(&:admin?).select(&:confirmed?).sample
     # TODO: remove condition after root_url changed to different path than
     # profile in routes.rb
     unless has_current_path?(edit_user_registration_path)
@@ -196,7 +196,15 @@ class UsersTest < ApplicationSystemTestCase
     assert_text t("devise.registrations.destroyed")
   end
 
-  test 'index forbidden for non admin' do
+  test "sole admin cannot delete profile" do
+    sign_in user: users(:admin)
+    unless has_current_path?(edit_user_registration_path)
+      first(:link_or_button, users(:admin).email).click
+    end
+    assert find(:button, t("users.registrations.edit.delete"))[:disabled]
+  end
+
+  test "index forbidden for non admin" do
     sign_in user: users.reject(&:admin?).select(&:confirmed?).sample
     visit users_path
     assert_title "Access is forbidden to this page (403)"