add assertion for soluteGramsProperty #210

phetsims · Oct 11, 2017 · 504827b · 504827b
1 parent 3545505
commit 504827b
Showing 1 changed file with 3 additions and 1 deletion.
diff --git a/js/concentration/model/ConcentrationSolution.js b/js/concentration/model/ConcentrationSolution.js
@@ -93,7 +93,9 @@ define( function( require ) {
     // @public {number} amount of solute, in grams
     this.soluteGramsProperty = new DerivedProperty( [ this.soluteProperty, this.soluteAmountProperty, this.precipitateAmountProperty ],
       function( solute, soluteAmount, precipitateAmount ) {
-        return solute.molarMass * ( soluteAmount - precipitateAmount );
+        var soluteGrams = solute.molarMass * ( soluteAmount - precipitateAmount );
+        assert && assert( soluteGrams >= 0, 'invalid soluteGrams: ' + soluteGrams );
+        return soluteGrams;
       }, {
         tandem: tandem.createTandem( 'soluteGramsProperty' ),
         units: 'grams',