NullableBooleansTest

class NullableBooleansTest {

    enum class Result { OK, NOT }

    private fun testNullableBooleanWhen(
        nullableBoolean: Boolean?,
        check: (Boolean?) -> Boolean,
        resulting: Result
    ) {
        val result = if (check(nullableBoolean)) {
            Result.OK
        } else {
            Result.NOT
        }
        assertEquals(resulting, result)
    }

    @Test fun forEqualsTrue() {
        val check: (Boolean?) -> Boolean = { nb -> nb == true }
        testNullableBooleanWhen(true, check, Result.OK)
        testNullableBooleanWhen(false, check, Result.NOT)
        testNullableBooleanWhen(null, check, Result.NOT)
    }

    @Test fun forEqualsFalse() {
        val check: (Boolean?) -> Boolean = { nb -> nb == false }
        testNullableBooleanWhen(false, check, Result.OK)
        testNullableBooleanWhen(true, check, Result.NOT)
        testNullableBooleanWhen(null, check, Result.NOT)
    }

    @Test fun forNotEqualsTrue() {
        val check: (Boolean?) -> Boolean = { nb -> nb != true }
        testNullableBooleanWhen(false, check, Result.OK)
        testNullableBooleanWhen(null, check, Result.OK)
        testNullableBooleanWhen(true, check, Result.NOT)
    }

    @Test fun forNotEqualsFalse() {
        val check: (Boolean?) -> Boolean = { nb -> nb != false }
        testNullableBooleanWhen(true, check, Result.OK)
        testNullableBooleanWhen(null, check, Result.OK)
        testNullableBooleanWhen(false, check, Result.NOT)
    }

    @Test fun forEqualsNull() {
        val check: (Boolean?) -> Boolean = { nb -> nb == null }
        testNullableBooleanWhen(null, check, Result.OK)
        testNullableBooleanWhen(false, check, Result.NOT)
        testNullableBooleanWhen(true, check, Result.NOT)
    }

    @Test fun forNotEqualsNull() {
        val check: (Boolean?) -> Boolean = { nb -> nb != null }
        testNullableBooleanWhen(false, check, Result.OK)
        testNullableBooleanWhen(true, check, Result.OK)
        testNullableBooleanWhen(null, check, Result.NOT)
    }
}