CalculatorTest.java

CalculatorTest.java

package com.clouway.calculator;

import org.jmock.Expectations;
import org.jmock.Mockery;
import org.testng.annotations.BeforeMethod;
import org.testng.annotations.Test;

import java.util.ArrayList;
import java.util.List;

public class CalculatorTest extends JMockFastTest {
  
  Mockery context = new Mockery();

  interface CalculationTextBox {
    void displayResult(Integer number);
  }

  class Calculator {

    private final CalculationTextBox calculationTextBox;

    private List<Integer> numbers = new ArrayList<Integer>(2);
    private String operation;

    public Calculator(CalculationTextBox calculationTextBox) {
      this.calculationTextBox = calculationTextBox;
    }

    public void onNumberPressed(Integer number) {
      numbers.add(number);
    }

    public void onOperationPressed(String operation) {
      this.operation = operation;
    }

    public void onCalculate() {
      if ("+".equals(operation)) {
        calculationTextBox.displayResult(numbers.get(0) + numbers.get(1));
      } else if ("-".equals(operation)) {
        calculationTextBox.displayResult(numbers.get(0) - numbers.get(1));
      } else if ("/".equals(operation)) {
        calculationTextBox.displayResult(numbers.get(0) / numbers.get(1));
      }

      // we need to be prepared for the next calculation
      operation = null;
      numbers.clear();
    }
  }

  private Calculator calculator;
  private CalculationTextBox calculationTextBox;

  @BeforeMethod
  public void initializeCalculator() {
    calculationTextBox = context.mock(CalculationTextBox.class);
    calculator = new Calculator(calculationTextBox);
  }

  @Test
  public void addTwoNumbers() {

    allowCalculationToReturnOnly(8);

    interpret(5, "+", 3);
  }

  @Test
  public void subtractTwoNumbers() {

    allowCalculationToReturnOnly(12);

    interpret(14, "-", 2);
  }

  @Test
  public void consistentCalculationsAreAllowed() {
    allowCalculationToReturnOnly(3);
    allowCalculationToReturnOnly(4);

    interpret(6, "/", 2);

    interpret(3, "+", 1);
  }

  private void interpret(int leftNumber, String operation, int rightNumber) {
    calculator.onNumberPressed(leftNumber);
    calculator.onOperationPressed(operation);
    calculator.onNumberPressed(rightNumber);

    calculator.onCalculate();
  }

  private void allowCalculationToReturnOnly(final Integer expectedValue) {
    context.checking(new Expectations() {{
      oneOf(calculationTextBox).displayResult(expectedValue);
    }});
  }
}