JUnit 4 -> 5

A sed script to aid migration from JUnit 4 to JUnit 5.

1. Download junit4-to-5.sed:

$(command -v wget && printf %s -O- || command -v curl) \
    https://raw.githubusercontent.com/tingstad/junit4to5/master/junit4-to-5.sed \
    > junit4-to-5.sed

2. Run script on java test files:

find . -path '*/src/test/*.java' -exec sed -Ei.bak -f junit4-to-5.sed {} \; -exec rm {}.bak \;

3. Update your pom.xml dependencies, see this example or the User Guide.

Finally, fix any remaining build failures manually (or create an issue for me :))

The script replaces:

Old	New
org.junit.Test	org.junit.jupiter.api.Test
org.junit.Assert	org.junit.jupiter.api.Assertions
@Before, @After	@BeforeEach, @AfterEach
@BeforeClass, @AfterClass	@BeforeAll, @AfterAll
@Ignore	@Disabled
@Category	@Tag
@RunWith	@ExtendWith
@Test(timeout=3000)	@Timeout(3)
@Test(expected=Ex.class) m(){ ...	@Test m(){ assertThrows(Ex.class, () -> ...
@RunWith(Parameterized.class), @Test	@ParameterizedTest
assertTrue/assertFalse("msg", val)	assertTrue/assertFalse(val, "msg")
assertNull/assertNotNull("msg", val)	assertNull/assertNotNull(val, "msg")
assertEquals(msg, expected, actual)	assert(Not)Equals(expected, actual, msg)
assertSame/NotSame(msg, expected, actual)	assert(Not)Same(expected, actual, msg)
assertArrayEquals(msg, expected, actual)	assertArrayEquals(expected, actual, msg)

Philosophy

1. Should only make changes with a high probability of being correct
2. Should not change unaffected lines and formatting
3. Should make changes non-breaking (compiling and passing) when possible
4. Should leave difficult problems to the humans and let the test fail to be easily detectable

Why sed?

1. It is almost ubiquitous, so the script has few dependencies and is easy to install and run
2. Does not re-format code (see Philosophy)
3. Simple search and replace is easy to implement
4. Fun challenge to do a bit more complex tasks

Limitations

1. Does not presume assertion library, leaving assertThat to fail
2. Does not parse arguments on multiple lines to shift the "message" parameter position of assertTrue/False/Equals
3. Probably many features still missing