Android data class unit test

Question

I have a data class below -

data class MyViewState(
    val loading: Boolean = false,
    val data: String? = null,
    val error: String? = null
)

I have a simple JUnit4 test -

@Test
fun testLoading() {
    val myViewState = MyViewState()
    myViewState.copy(loading = true)
    assertEquals(myViewState.loading, true)
}

The test fails. Gives me -

java.lang.AssertionError: 
Expected :false
Actual   :true

Answer 1

You are checking the value in the original object. Use this:

@Test
fun testLoading() {
    val myViewState = MyViewState()
    val myViewStateCopy = myViewState.copy(loading = true)
    assertEquals(true, myViewStateCopy.loading)
}

Also note your expected value should be the first parameter to assertEquals()