Tests passing, all formulas validated

.gitignore

@@ -11,3 +11,5 @@
 .local/
 .zcompdump
 .zshrc
+.idea
+/d4rt-formulas.iml

README.md

@@ -5,7 +5,6 @@ A comprehensive command-line application for managing and computing mathematical
 This project uses dart language, and flutter framework. It leverages d4rt library to execute formulas.
 
 
-
 # Development guidelines
 If you are a contributor or an agent, please follow [CLAUDE.md](./CLAUDE.md) for development guidelines.
 

lib/formula_evaluator.dart

@@ -32,7 +32,7 @@ class FormulaEvaluator {
 
   /// Evaluates a formula with the given input values.
   /// 
-  /// The [formula] must have exactly one output variable.
+  /// The [formula] must have exactly one output variable (validated during construction).
   /// The [inputValues] map must contain values for all input variables defined
   /// in the formula.
   /// 
@@ -48,11 +48,9 @@ class FormulaEvaluator {
   /// Returns the computed value of the single output variable.
   /// 
   /// Throws [FormulaEvaluationException] if:
-  /// - The formula has zero or more than one output variable
   /// - Required input variables are missing
   /// - The d4rt code execution fails
   dynamic evaluate(Formula formula, Map<String, dynamic> inputValues) {
-    _validateFormula(formula);
     _validateInputValues(formula, inputValues);
 
     try {
@@ -71,16 +69,6 @@ class FormulaEvaluator {
     }
   }
 
-  /// Validates that the formula has exactly one output variable
-  void _validateFormula(Formula formula) {
-    if (formula.output.length != 1) {
-      throw FormulaEvaluationException(
-        'Formula "${formula.name}" must have exactly one output variable, '
-        'but has ${formula.output.length}',
-      );
-    }
-  }
-
   /// Validates that all required input variables are provided
   void _validateInputValues(Formula formula, Map<String, dynamic> inputValues) {
     final missingVars = <String>[];
@@ -101,13 +89,13 @@ class FormulaEvaluator {
 
   /// Gets the name of the single output variable from the formula
   String getOutputVariableName(Formula formula) {
-    _validateFormula(formula);
+    // Formula construction already ensures exactly one output variable
     return formula.output.keys.first;
   }
 
   /// Gets the magnitude of the single output variable from the formula
   String getOutputVariableMagnitude(Formula formula) {
-    _validateFormula(formula);
+    // Formula construction already ensures exactly one output variable
     return formula.output.values.first.magnitude;
   }
 

lib/formula_models.dart

@@ -46,12 +46,26 @@ class Formula {
   final Map<String, VariableSpec> output; // Supports multiple output variables
   final String d4rtCode;
 
-  const Formula({
+  Formula({
     required this.name,
     required this.input,
     required this.output,
     required this.d4rtCode,
-  });
+  }){
+    validate();
+  }
+
+  validate() {
+    if (name.trim().isEmpty) {
+      throw ArgumentError('Formula name cannot be empty');
+    }
+    if (output.length != 1) {
+      throw ArgumentError(
+        'Formula "$name" must have exactly one output variable, '
+        'but has ${output.length}',
+      );
+    }
+  }
 
   factory Formula.fromJson(Map<String, dynamic> json) {
     final name = json['name'];

test/formula_evaluator_test.dart

@@ -18,9 +18,7 @@ void main() {
             'm': VariableSpec(magnitude: 'mass'),
             'a': VariableSpec(magnitude: 'acceleration'),
           },
-          output: {
+          output: {'F': VariableSpec(magnitude: 'force')},
-            'F': VariableSpec(magnitude: 'force'),
-          },
           d4rtCode: '''
             main() {
               return a * m;
@@ -43,9 +41,7 @@ void main() {
             'x': VariableSpec(magnitude: 'scalar'),
             'y': VariableSpec(magnitude: 'scalar'),
           },
-          output: {
+          output: {'result': VariableSpec(magnitude: 'scalar')},
-            'result': VariableSpec(magnitude: 'scalar'),
-          },
           d4rtCode: '''
             main() {
               return x + y;
@@ -53,10 +49,7 @@ void main() {
           ''',
         );
 
-        final result = evaluator.evaluate(formula, {
+        final result = evaluator.evaluate(formula, {'x': 5, 'y': 3});
-          'x': 5,
-          'y': 3,
-        });
 
         expect(result, 8);
       });
@@ -64,12 +57,8 @@ void main() {
       test('handles single input variable', () {
         final formula = Formula(
           name: 'Square function',
-          input: {
+          input: {'n': VariableSpec(magnitude: 'scalar')},
-            'n': VariableSpec(magnitude: 'scalar'),
+          output: {'result': VariableSpec(magnitude: 'scalar')},
-          },
-          output: {
-            'result': VariableSpec(magnitude: 'scalar'),
-          },
           d4rtCode: '''
             main() {
               return n * n;
@@ -89,9 +78,7 @@ void main() {
             'b': VariableSpec(magnitude: 'scalar'),
             'c': VariableSpec(magnitude: 'scalar'),
           },
-          output: {
+          output: {'discriminant': VariableSpec(magnitude: 'scalar')},
-            'discriminant': VariableSpec(magnitude: 'scalar'),
-          },
           d4rtCode: '''
             main() {
               return b * b - 4 * a * c;
@@ -99,11 +86,7 @@ void main() {
           ''',
         );
 
-        final result = evaluator.evaluate(formula, {
+        final result = evaluator.evaluate(formula, {'a': 1, 'b': 5, 'c': 6});
-          'a': 1,
-          'b': 5,
-          'c': 6,
-        });
 
         expect(result, 1); // b² - 4ac = 25 - 24 = 1
       });
@@ -118,9 +101,7 @@ void main() {
             'a': VariableSpec(magnitude: 'scalar'),
             'b': VariableSpec(magnitude: 'scalar'),
           },
-          output: {
+          output: {'result': VariableSpec(magnitude: 'scalar')},
-            'result': VariableSpec(magnitude: 'scalar'),
-          },
           d4rtCode: 'main() { return a + b + z; }',
         );
 
@@ -136,9 +117,7 @@ void main() {
             'a': VariableSpec(magnitude: 'scalar'),
             'y': VariableSpec(magnitude: 'scalar'),
           },
-          output: {
+          output: {'result': VariableSpec(magnitude: 'scalar')},
-            'result': VariableSpec(magnitude: 'scalar'),
-          },
           d4rtCode: '''
             main() {
               // Variables: a=1, y=2, z=3
@@ -147,47 +126,44 @@ void main() {
           ''',
         );
 
-        final result = evaluator.evaluate(formula, {
+        final result = evaluator.evaluate(formula, {'z': 3, 'a': 1, 'y': 2});
-          'z': 3,
-          'a': 1,
-          'y': 2,
-        });
 
         expect(result, 123); // 1*100 + 2*10 + 3 = 123
       });
     });
 
     group('Error handling', () {
-      test('throws exception for formula with no output variables', () {
+      test(
-        final formula = Formula(
+        'throws exception for formula with no output variables during construction',
+        () {
+          expect(() {
+            return Formula(
               name: 'Invalid formula',
               input: {'x': VariableSpec(magnitude: 'scalar')},
               output: {}, // No output variables
               d4rtCode: 'main() { return x; }',
             );
-
+          }, throwsA(isA<ArgumentError>()));
-        expect(
+        },
-          () => evaluator.evaluate(formula, {'x': 1}),
-          throwsA(isA<FormulaEvaluationException>()),
       );
-      });
 
-      test('throws exception for formula with multiple output variables', () {
+      test(
-        final formula = Formula(
+        'throws exception for formula with multiple output variables during construction',
+        () {
+          expect(
+            () => Formula(
               name: 'Invalid formula',
               input: {'x': VariableSpec(magnitude: 'scalar')},
               output: {
                 'y': VariableSpec(magnitude: 'scalar'),
                 'z': VariableSpec(magnitude: 'scalar'),
               },
-          d4rtCode: 'main(x) { return x; }',
+              d4rtCode: 'main() { return x; }',
+            ),
+            throwsA(isA<ArgumentError>()),
           );
-
+        },
-        expect(
-          () => evaluator.evaluate(formula, {'x': 1}),
-          throwsA(isA<FormulaEvaluationException>()),
       );
-      });
 
       test('throws exception for missing input variables', () {
         final formula = Formula(
@@ -233,7 +209,9 @@ void main() {
         expect(evaluator.getOutputVariableName(formula), 'force');
       });
 
-      test('getOutputVariableMagnitude returns the output variable magnitude', () {
+      test(
+        'getOutputVariableMagnitude returns the output variable magnitude',
+        () {
           final formula = Formula(
             name: 'Test',
             input: {'x': VariableSpec(magnitude: 'scalar')},
@@ -242,24 +220,44 @@ void main() {
           );
 
           expect(evaluator.getOutputVariableMagnitude(formula), 'Newton');
+        },
+      );
+
+      test('utility methods work correctly with valid formulas', () {
+        final validFormula = Formula(
+          name: 'Valid Formula',
+          input: {'x': VariableSpec(magnitude: 'scalar')},
+          output: {'result': VariableSpec(magnitude: 'Newton')},
+          d4rtCode: 'main() { return x; }',
+        );
+
+        expect(evaluator.getOutputVariableName(validFormula), 'result');
+        expect(evaluator.getOutputVariableMagnitude(validFormula), 'Newton');
       });
 
-      test('utility methods throw exception for invalid formulas', () {
+      test('validates formula construction with factory method', () {
-        final invalidFormula = Formula(
+        // Test the factory method validation
+        expect(
+          () => Formula(
             name: 'Invalid',
             input: {'x': VariableSpec(magnitude: 'scalar')},
             output: {}, // No output variables
             d4rtCode: 'main() { return x; }',
+          ),
+          throwsA(isA<ArgumentError>()),
         );
 
         expect(
-          () => evaluator.getOutputVariableName(invalidFormula),
+          () => Formula(
-          throwsA(isA<FormulaEvaluationException>()),
+            name: 'Invalid',
-        );
+            input: {'x': VariableSpec(magnitude: 'scalar')},
-
+            output: {
-        expect(
+              'y': VariableSpec(magnitude: 'scalar'),
-          () => evaluator.getOutputVariableMagnitude(invalidFormula),
+              'z': VariableSpec(magnitude: 'scalar'),
-          throwsA(isA<FormulaEvaluationException>()),
+            },
+            d4rtCode: 'main() { return x; }',
+          ),
+          throwsA(isA<ArgumentError>()),
         );
       });
     });