Updated m3_12_testCalculateWorksCorrectly with constructor check

src/test/java/com/h2/Module3_Test.java

@@ -288,6 +288,10 @@ public void m3_12_testCalculateWorksCorrectly() throws IllegalAccessException, I
         float[] credits = new float[]{10.0f, 20.0f};
         float[] debits = new float[]{5.0f};
         final Constructor<?> constructor = constructors[0];
+
+        int parameterCount = constructor.getParameterCount();
+        assertEquals(2, parameterCount, classToFind + " must have a constructor with 2 parameters - credits and debits, both should be of type 'float[]'");
+
         Object instance = constructor.newInstance(credits, debits);
         final Method[] methods = savingsCalculator.getDeclaredMethods();
         final List<Method> filteredMethod = Arrays.stream(methods).filter(method -> method.getName().equals(methodName)).collect(Collectors.toList());