JUnit 4 -> 5

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

find ./src/ -name \*.java -exec sed -E -i.bak -f junit4-to-5.sed {} \; -exec rm {}.bak \;

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(expected=Ex.class) m(){ ...`	`@Test m(){ assertThrows(Ex.class, () -> ...`
`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)`

Motivation

Save a ton of work by employing a re-usable script instead of repeating manual chores.

How to use

Download and run file junit4-to-5.sed on all java test files:

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

find ./src/test/ -name \*.java -exec sed -E -i.bak -f junit4-to-5.sed {} \; -exec rm {}.bak \;

Then 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 :))

Philosophy

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

Why sed?

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

Limitations