diff --git a/lib/body_tracking/formula.rb b/lib/body_tracking/formula.rb
index 2b5f943..3f38e81 100644
--- a/lib/body_tracking/formula.rb
+++ b/lib/body_tracking/formula.rb
@@ -14,13 +14,6 @@ module BodyTracking
       end
 
       def validate
-        # TODO: add tests
-        # failing test vectors:
-        # - fcall disallowed: "abs(Fats)+Energy < 10"
-        # working test vectors:
-        #   ((Energy-Calculated)/Energy).abs > 0.2
-        #   Fats.nil? || Fats/Proteins > 2
-
         parser = FormulaBuilder.new(@formula)
         identifiers, parts = parser.parse
         errors = parser.errors
@@ -191,7 +184,7 @@ module BodyTracking
               [right[1], :unknown_method]
             end
           else
-            raise NotImplementedError
+            raise NotImplementedError, right.inspect
           end
 
         case left[0]
@@ -211,7 +204,7 @@ module BodyTracking
           else
             [:bt_numeric_method_call, "#{left[1]}#{dot.to_s}#{method}"]
           end
-        when :bt_numeric_method_call
+        when :bt_numeric_method_call, :bt_expression
           if mtype == :quantity_method
             # TODO: add error reporting
             raise NotImplementedError
@@ -219,7 +212,7 @@ module BodyTracking
             [:bt_numeric_method_call, "#{left[1]}#{dot.to_s}#{method}"]
           end
         else
-          raise NotImplementedError
+          raise NotImplementedError, left.inspect
         end
       end
 
@@ -279,10 +272,18 @@ module BodyTracking
         [:bt_quantity, token]
       end
 
+      def on_float(token)
+        [:bt_expression, token]
+      end
+
       def on_ident(token)
         [:bt_ident, token]
       end
 
+      def on_int(token)
+        [:bt_expression, token]
+      end
+
       def on_kw(token)
         @disallowed[:keyword] << token unless token == 'nil'
       end
@@ -295,10 +296,12 @@ module BodyTracking
         stmts.map do |stmt|
           ttype, token = stmt
           case ttype
-          when :bt_expression
+          when :bt_expression, :bt_numeric_method_call
             token
+          when :bt_quantity
+            "quantities['#{token}'][_index]"
           else
-            raise NotImplementedError
+            raise NotImplementedError, stmt.inspect
           end
         end.join(';')
       end
diff --git a/test/unit/formula_test.rb b/test/unit/formula_test.rb
index 76e9571..7446b9b 100644
--- a/test/unit/formula_test.rb
+++ b/test/unit/formula_test.rb
@@ -7,14 +7,61 @@ class FormulaTest < ActiveSupport::TestCase
   end
 
   def test_builder_parses_valid_formulas_properly
+    # TODO: add tests
+    # failing test vectors:
+    # - fcall disallowed: "abs(Fats)+Energy < 10"
+
     vector = [
+      # Non-quantity expressions
       '4', Set[], [
-        {type: :indexed, content: '4*2'}
+        {type: :indexed, content: "4"}
+      ],
+      '3.2', Set[], [
+        {type: :indexed, content: "3.2"}
+      ],
+      '4 * 2', Set[], [
+        {type: :indexed, content: "4*2"}
+      ],
+      '7.3 * 2.1', Set[], [
+        {type: :indexed, content: "7.3*2.1"}
+      ],
+      '7 * 2.1', Set[], [
+        {type: :indexed, content: "7*2.1"}
       ],
 
-      #'4*2'
-      #'Fats'
-      #'fats'
+      # Quantity expressions
+      'Fats', Set['Fats'], [
+        {type: :indexed, content: "quantities['Fats'][_index]"}
+      ],
+      'fats', Set['fats'], [
+        {type: :indexed, content: "quantities['fats'][_index]"}
+      ],
+      '2 * Fats', Set['Fats'], [
+        {type: :indexed, content: "2*quantities['Fats'][_index]"}
+      ],
+      '4*Proteins + 9*Fats + 4*Carbohydrates', Set['Proteins', 'Fats', 'Carbohydrates'], [
+        {type: :indexed, content: "4*quantities['Proteins'][_index]+" \
+         "9*quantities['Fats'][_index]+4*quantities['Carbohydrates'][_index]"}
+      ],
+      'Weight * (Fats + 0.2)', Set['Weight', 'Fats'], [
+        {type: :indexed, content: "quantities['Weight'][_index]*" \
+         "(quantities['Fats'][_index]+0.2)"}
+      ],
+
+      # Numeric method calls
+      'Fats.nil?', Set['Fats'], [
+        {type: :indexed, content: "quantities['Fats'][_index].nil?"}
+      ],
+      '((Energy-Calculated)/Energy).abs', Set['Energy', 'Calculated'], [
+        {type: :indexed, content: "((quantities['Energy'][_index]-" \
+         "quantities['Calculated'][_index])/quantities['Energy'][_index]).abs"}
+      ],
+
+      # Conditional expressions
+      'Fats.nil? || Fats/Proteins > 2', Set['Fats', 'Proteins'], [
+        {type: :indexed, content: "quantities['Fats'][_index].nil?||" \
+         "quantities['Fats'][_index]/quantities['Proteins'][_index]>2"}
+      ],
     ]
 
     vector.each_slice(3) do |formula, identifiers, parts|