Use Settings in Unit Testing

[kostapostolakis]

Hello, I have created this helper to save userName in Settings. I get and set the details in some viewModels.

class SettingsHelper {
    companion object {
        // User Data
        const val USER_NAME = "userName"
    }

    var userName: String?
        get() { return Settings().getStringOrNull(USER_NAME) }
        set(value) { Settings()[USER_NAME] = value }
}

I created the following unit test:

class EditProfileTest {
    @Test
    fun test_dataHaveChanged() {
        SettingsHelper().userName = "My Name"

        val editProfileViewModel = EditProfileViewModel()

        // When no changes, method returns false
        assertFalse(editProfileViewModel.dataHaveChanged())

        // When the userName is empty, method returns false
        editProfileViewModel.updateUserName("")
        assertFalse(editProfileViewModel.dataHaveChanged())
    }
}

And I get this error:

java.lang.NullPointerException
	at com.russhwolf.settings.NoArgKt.Settings(NoArg.kt:32)
	at gr.palermonights.mobileapp.helpers.SettingsHelper.setUserName(SettingsHelper.kt:48)
	at gr.palermonights.mobileapp.EditProfileTest.test_dataHaveChanged(EditProfileTest.kt:12)
	at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
	at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
	at java.base/java.lang.reflect.Method.invoke(Unknown Source)
	at org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:59)
	at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:12)
	at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:56)
	at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:17)
	at org.junit.runners.ParentRunner$3.evaluate(ParentRunner.java:306)
	at org.junit.runners.BlockJUnit4ClassRunner$1.evaluate(BlockJUnit4ClassRunner.java:100)
	at org.junit.runners.ParentRunner.runLeaf(ParentRunner.java:366)
	at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:103)
	at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:63)
	at org.junit.runners.ParentRunner$4.run(ParentRunner.java:331)
	at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:79)
	at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:329)
	at org.junit.runners.ParentRunner.access$100(ParentRunner.java:66)
	at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:293)
	at org.junit.runners.ParentRunner$3.evaluate(ParentRunner.java:306)
	at org.junit.runners.ParentRunner.run(ParentRunner.java:413)
	at org.gradle.api.internal.tasks.testing.junit.JUnitTestClassExecutor.runTestClass(JUnitTestClassExecutor.java:112)
	at org.gradle.api.internal.tasks.testing.junit.JUnitTestClassExecutor.execute(JUnitTestClassExecutor.java:58)
	at org.gradle.api.internal.tasks.testing.junit.JUnitTestClassExecutor.execute(JUnitTestClassExecutor.java:40)
	at org.gradle.api.internal.tasks.testing.junit.AbstractJUnitTestClassProcessor.processTestClass(AbstractJUnitTestClassProcessor.java:60)
	at org.gradle.api.internal.tasks.testing.SuiteTestClassProcessor.processTestClass(SuiteTestClassProcessor.java:52)
	at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
	at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
	at java.base/java.lang.reflect.Method.invoke(Unknown Source)
	at org.gradle.internal.dispatch.ReflectionDispatch.dispatch(ReflectionDispatch.java:36)
	at org.gradle.internal.dispatch.ReflectionDispatch.dispatch(ReflectionDispatch.java:24)
	at org.gradle.internal.dispatch.ContextClassLoaderDispatch.dispatch(ContextClassLoaderDispatch.java:33)
	at org.gradle.internal.dispatch.ProxyDispatchAdapter$DispatchingInvocationHandler.invoke(ProxyDispatchAdapter.java:94)
	at jdk.proxy1/jdk.proxy1.$Proxy2.processTestClass(Unknown Source)
	at org.gradle.api.internal.tasks.testing.worker.TestWorker$2.run(TestWorker.java:176)
	at org.gradle.api.internal.tasks.testing.worker.TestWorker.executeAndMaintainThreadName(TestWorker.java:129)
	at org.gradle.api.internal.tasks.testing.worker.TestWorker.execute(TestWorker.java:100)
	at org.gradle.api.internal.tasks.testing.worker.TestWorker.execute(TestWorker.java:60)
	at org.gradle.process.internal.worker.child.ActionExecutionWorker.execute(ActionExecutionWorker.java:56)
	at org.gradle.process.internal.worker.child.SystemApplicationClassLoaderWorker.call(SystemApplicationClassLoaderWorker.java:113)
	at org.gradle.process.internal.worker.child.SystemApplicationClassLoaderWorker.call(SystemApplicationClassLoaderWorker.java:65)
	at worker.org.gradle.process.internal.worker.GradleWorkerMain.run(GradleWorkerMain.java:69)
	at worker.org.gradle.process.internal.worker.GradleWorkerMain.main(GradleWorkerMain.java:74)

How can I use the helper in Unit Testing?

[russhwolf]

Calling the Settings() factory function invokes SharedPreferences APIs on Android, which aren't available in unit tests. Starting in 1.2 it will be possible to call SettingsInitializer().create(context) with a robolectric or other mock Context object for unit testing. Otherwise, you can inject a Settings object rather than hardcoding the Settings() call, and pass MapSettings() in tests.

[SirFilbido]

Calling the factory function invokes APIs on Android, which aren't available in unit tests. Starting in 1.2 it will be possible to call with a robolectric or other mock object for unit testing. Otherwise, you can inject a object rather than hardcoding the call, and pass in tests.Settings()``SharedPreferences``SettingsInitializer().create(context)``Context``Settings``Settings()``MapSettings()

Hey guys,

I didn't quite understand the answer. In my case, I'm doing unit testing at CommonMainTest in KMP(old KMM). I tried using KoinTest and Mockative and both returned the same error presented initially.

@russhwolf could you explain better how to resolve this issue when testing?

[zivkovic]

Is there a timeframe for when 1.2 would be released?

[russhwolf]

1.2 is now out. You can now do something like this in a test

val context: Context = ...
SettingsInitializer().create(context)

val settings = Settings()
// do something with settings

Alternatively, make your helper class injectable:

class SettingsHelper(val settings: Settings = Settings()) {
    companion object {
        // User Data
        const val USER_NAME = "userName"
    }

    var userName: String?
        get() { return settings.getStringOrNull(USER_NAME) }
        set(value) { settings[USER_NAME] = value }
}

then you can do SettingsHelper(MapSettings()) in your tests.