Unit Testing Series #3

4 min readOct 13, 2022

In this article, I am going to explore the building blocks to understand how to enter into testing world of Android app.

Annotations that are building Blocks of Unit test class

@Test : This is the annotation that will make any method to be run under Junit. Once you add @Test annotation you will be able to test any existing functionality.
@Before : This is the annotation that will be used for pre-requisite for any unit test methods. This method will be executed before executing any @test method of any test class. It is recommended to use @Before method when you have scenario’s like a particular class instance is going to reuse in many test methods then initialize it in @Before method will be a best choice.
@After : This is the annotation that will be used after all the test method of a test class. @After annotation method can be used for tear down feature like shutdown feature. This is also very important to keep your variables reset once unit testing done.

Steps to test a simple feature in android

Step 1 : Write your feature class like I have a feature for register a user.

object ValidateRegistrationInput {

    private val existingUsers = listOf("Abhishek", "Kai", "Jason")

    fun isValidRegistrationInput(
        username: String,
        password: String,
        confirmPassword: String
    ): Boolean {
        if (username.isEmpty() || password.isEmpty() || confirmPassword.isEmpty()) {
            return false
        }
        if (username in existingUsers) {
            return false
        }
        if (password != confirmPassword) {
            return false
        }
        if (password.count { it.isDigit() } < 6) {
            return false
        }
        return true
    }
}

Step 2: Let’s have a testing class so for that right click on the existing feature class and click on generate.

Step 3 : Click on Test that will ask you next steps

Step 4: After that a pop up came that will show a suggestion of your test class and few methods options to generate like @Before and @After. Click Ok.

Step 5: Now you got another popup that is for picking folder for test. By default all the local test should be tested under test folder while UI & Integration test should be created under androidTest folder.

Step 6: Write all the test cases required to test the feature end to end

internal class ValidateRegistrationInputTest {

    @Test
    fun `When username is empty Then return false`() {
        val output = ValidateRegistrationInput.isValidRegistrationInput(
            EMPTY_STRING,
            TEST_PASSWORD,
            TEST_CONFIRMED_PASSWORD
        )

        assertFalse(output)
    }

    @Test
    fun `When username, password, confirmedPassword is correct Then return true`() {
        val output = ValidateRegistrationInput.isValidRegistrationInput(
            TEST_USERNAME,
            TEST_PASSWORD,
            TEST_CONFIRMED_PASSWORD
        )

        assertTrue(output)
    }

    @Test
    fun `When username already exists Then return false`() {
        val output = ValidateRegistrationInput.isValidRegistrationInput(
            TEST_EXISTING_USERNAME,
            TEST_PASSWORD,
            TEST_CONFIRMED_PASSWORD
        )

        assertFalse(output)
    }

    @Test
    fun `When wrong confirmPassword entered Then return false`() {
        val output = ValidateRegistrationInput.isValidRegistrationInput(
            TEST_USERNAME,
            TEST_PASSWORD,
            TEST_WRONG_CONFIRMED_PASSWORD
        )

        assertFalse(output)
    }

    @Test
    fun `When Password is less than six char Then return false`() {
        val output = ValidateRegistrationInput.isValidRegistrationInput(
            TEST_USERNAME,
            TEST_INVALID_PASSWORD,
            TEST_CONFIRMED_PASSWORD
        )

        assertFalse(output)
    }

    @Before
    fun setUp() {
        //This is the method where you can initialize the variable and use them for all test methods.
    }

    @After
    fun tearDown() {
        // this method is used to unMock all the used variable or used as tear down feature 
    }

    private companion object {
        const val TEST_USERNAME = "test"
        const val TEST_PASSWORD = "12345678"
        const val TEST_INVALID_PASSWORD = "1234"
        const val TEST_CONFIRMED_PASSWORD = "12345678"
        const val TEST_WRONG_CONFIRMED_PASSWORD = "123456789"
        const val EMPTY_STRING = ""
        const val TEST_EXISTING_USERNAME = "Abhishek"
    }
}