Test expected exceptions in Kotlin

Question

In Java, the programmer can specify expected exceptions for JUnit test cases like this:

@Test(expected = ArithmeticException.class)
public void omg()
{
    int bl         


        

Answer 1

The Kotlin translation of the Java example for JUnit 4.12 is:

@Test(expected = ArithmeticException::class)
fun omg() {
    val blackHole = 1 / 0
}

However, JUnit 4.13 introduced two assertThrows methods for finer-granular exception scopes:

@Test
fun omg() {
    // ...
    assertThrows(ArithmeticException::class.java) {
        val blackHole = 1 / 0
    }
    // ...
}

Both assertThrows methods return the expected exception for additional assertions:

@Test
fun omg() {
    // ...
    val exception = assertThrows(ArithmeticException::class.java) {
        val blackHole = 1 / 0
    }
    assertEquals("/ by zero", exception.message)
    // ...
}