Andrei Solntsev
29 Oct 2010

Unit-test evolution

Antud lugu on saadaval ainult inglise keeles

This is an example of unit-test evolution which I presented on recent devclub.eu workshop.Let’s consider 3 revisions of the same unit-test class.This is the first revision of this class:


public class ReferenceNumberTest {
  @Test
  public void testValidate() {
    assertFalse( ReferenceNumber.validate("1234567890123") );
    assertFalse( ReferenceNumber.validate("1234567") );
    assertTrue( ReferenceNumber.validate("12345678") );
  }
}

We call it a typical unit-test.At some moment, some developer decides to apply some TDD best practices and split this test-method into 3 with some meaningful names.This is what he got:


public class ReferenceNumberTest {
  @Test
  public void testTooLong() {
    String len13 = "1234567891111";
    assertEquals(len13.length(), 13);
    assertEquals(ReferenceNumber.validate(len13), false);
  }


  @Test
  public void testTooShort() {
    String len7 = "1234567";
    assertEquals(len7.length(), 7);
    assertEquals(ReferenceNumber.validate(len7), false);
  }


  @Test
  public void testOk() {
    String len8 = "12345678";
    assertEquals(len8.length(), 8);
    assertEquals(ReferenceNumber.validate(len8), true);


    String len12 = "123456789111";
    assertEquals(len12.length(), 12);
    assertEquals(ReferenceNumber.validate(len12), true);
  }
}

We call it good unit-test.After some time, some developer decides that even this good unit-test is not human-readable and does not provide enough information about how class ReferenceNumber should work. He continued splitting and renaming.This is what he got at the end:


public class ReferenceNumberTest {
  @Test
  public void nullIsNotValidReferenceNumber() {
    assertFalse(ReferenceNumber.validate(null));
  }


  @Test
  public void referenceNumberShouldBeShorterThan13() {
    assertFalse(ReferenceNumber.validate("1234567890123"));
  }


  @Test
  public void referenceNumberShouldBeLongerThan7() {
    assertFalse(ReferenceNumber.validate("1234567"));
  }


  @Test
  public void referenceNumberShouldContainOnlyNumbers() {
    assertFalse(ReferenceNumber.validate("1234567ab"));
    assertFalse(ReferenceNumber.validate("abcdefghi"));
    assertFalse(ReferenceNumber.validate("---------"));
    assertFalse(ReferenceNumber.validate(" "));
  }


  @Test
  public void validReferenceNumberExamples() {
    assertTrue(ReferenceNumber.validate("12345678"));
    assertTrue(ReferenceNumber.validate("123456789"));
    assertTrue(ReferenceNumber.validate("1234567890"));
    assertTrue(ReferenceNumber.validate("12345678901"));
    assertTrue(ReferenceNumber.validate("123456789012"));
  }
}

We call it BDD style specification.And finally, the most interesting part. During preparing for the workshop, I have discovered that I haven’t copied the original source code of the class ReferenceNumber being tested. Panic! One day left! I had to urgently re-create it from scratch!Now look at these 3 test-classes, and imagine, which of them helped me to create class ReferenceNumber.

Our recent stories

Weekly TeX - how knowledge sharing shapes our culture

Weekly Technology Exchange (TeX) sessions are an integral part of Codeborne’s DNA. These sessions provide our team with the opportunity to share new knowledge, present interesting discoveries, and discuss the latest technological advancements.

The story of HIIT Pekk

At Codeborne, we believe that work should be balanced with fun and fitness. Our journey with high-intensity interval training (HIIT) began as a creative response to the challenges posed by the COVID-19 pandemic.