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Test Methods

A test class itself does not do anything. We need methods for JUnit to run.

@Test Annotation

All test methods must have the annotation @Test before them. This tells JUnit to run this method.

annotation

A marker in source code that provides data about the program. It is read by the compiler or the program using the code. Examples:

  • @Override
  • @Test
  • @SuppressWarnings

Method Purpose

Each test method should call one of the methods of the class being tested, and usually test for one specific thing.

The test method tests a single application method's result.

@Test
public void test_addExclamations_add_correct_number_of_exclamations() {
  StringManipulator sm = new StringManipulator();
  String input = "hello";
  String expected = "hello!!!";
  String output = sm.addExclamations(input, 3);  // single StringManipulator method call
  assertEquals(expected, output);
}

Naming, Return Type, and Parameters

Name the method using snake_case or camelCase (snake case is easier to read).

The method should include which method it tests, and what condition it is testing - long, descriptive method names are fine.

Test method names usually begin with test (which was a requirement from an older version of JUnit, and has become convention now.)

Return type is always void, and the test method takes no parameters.

@Test
public void test_convertToArray_splits_String_into_array_on_char(){
  // ...
}

Method Body

The method body will set up test conditions, and call a single method.

It compares an expected result to the method's actual result using JUnit assert methods.

  • These methods say whether a test passes or fails.
@Test
public void test_addExclamations_add_correct_number_of_exclamations() {
  StringManipulator sm = new StringManipulator();
  String input = "hello";
  String expected = "hello!!!";
  String output = sm.addExclamations(input, 3);
  assertEquals(expected, output); // assert statement
}

Methods Are Independent

Test methods never depend on each other.

  • We cannot guarantee the order in which JUnit will run test methods.
  • Test method A cannot depend on some effect of test method B.

Drill

In this drill you will be creating methods in TextConverterTests to test the TextConverter methods. The purpose is to name the methods correctly, and remember to annotate them with @Test. UnitTesting/src/com.example.unittesting.drills.TextConverter

UnitTesting/test/com.example.unittesting.drills.TextConverterTests

  • toCaps
  • returns null for a null input String.
  • returns all caps version of input String.
  • removeOuterWhitespace
  • returns null for a null input String.
  • returns String with outer whitespace removed.
  • returns String with inner whitespace intact.
  • concatStrings
  • returns null for a null input String.
  • returns empty String for no input.
  • returns empty String for empty String input.
  • returns single String same length as input String
  • returns two Strings concatenated without extra whitespace.
  • returns two Strings concatenated with whitespace intact.

(Solution:TextConverterTests2.java )

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