code_coverage_11.java

@RunWith(Parameterized.class)
public class CalculatorTest {
  @Parameters(name = "{index}: CalculatorTest({0})={1}, throws {2}")
  public static Collection<Object[]> data() {
    return Arrays.asList(new Object[][]{
      {"1 + 1", 2, null},
      {"1 + 1 + 1", 3, null},
      {"1–1", 0, null},
      {"1 * 1", 1, null},
      {"1 / 1", 1, null},
      {"( 1 + 1 )", 2, null},
      {"+", 0, new CalculatorException("Invalid expression: +")},
      {"1 1", 0, new CalculatorException("Invalid expression: 1 1")}
    });
  }

  private final String input;
  private final double expected;
  private final Exception exception;
  
  public CalculatorTest(String input, double expected, Exception exception) {
    this.input = input;
    this.expected = expected;
    this.exception = exception;
  }
  
  @Test
  public void testProcess() {
    Calculator c = new CalculatorImpl();
    try {
      double result = c.process(input);
      if (exception != null) {
        fail("should have thrown an exception: " + exception);
      }
      // shouldn't compare doubles without a delta, because FP math isn't accurate
      assertEquals(expected, result, 0.000001);
    } catch (Exception e) {
      if (exception == null) {
        fail("should not have thrown an exception, but threw " + e);
      }
      if (!exception.getClass().equals(e.getClass()) || !exception.getMessage().equals(e.getMessage())) {
        fail("expected exception " + exception + "; got exception " + e);
      }
    }
  }
}