TL;DR: Testing is important!

In Java, Unit Tests are commonly provided by the JUnit library

Have a look at this cheat-sheet:

Source: https://jrebel.com/rebellabs/junit-cheat-sheet/

  • Each test should be independent, and not rely on each other

  • Each test should have some variant of a test decorator

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    @Test
void myCoolTest() {
// doStuff();
}

  • fail() - instantly fail a test

  • fail(String message) - instantly fail a test with a message

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    @Test
void doTheThing() {
// doMoreStuff()
if (result != 6) {
fail();
}
}

  • assertTrue()

  • assertFalse()

  • assertEqual(expected, value)

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    void checkThatThing() {
assertTrue(obj.hasThingy());
assertFalse(obj.isRound());
  
assertEqual(6, obj.getValue());
assertTrue(obj.getValue() == 6); // Also the same

// Though as usual, String comparisons _require_ the .equals() construction
assertEqual("Pan", obj.getText());
// FAIL (probably): assertTrue("Pan" == obj.getText());
}

Parameterised Testing

You can systematically supply arguments into your test cases. These arguments can be sourced from an iterable value in the testing file.

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@ParamaterisedTest
@MethodSoure(value = "data")
void test(int arg) {
  // doStuff();
}

public static int[] data() {
  return new int[] {5,3,10,2,20,42 };
}