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Testing RxAndroid Plugin Scheduler Management in ReactiveX/RxAndroid

This test suite validates the RxAndroidPlugins functionality without Robolectric dependency, specifically focusing on scheduler manipulation and plugin reset capabilities. The tests ensure proper handling of main thread scheduler replacement in RxAndroid.

Test Coverage Overview

The test coverage focuses on the core plugin manipulation functionality in RxAndroid, specifically the ability to replace the main thread scheduler.

Key areas tested include:

Plugin reset functionality
Main thread scheduler replacement
Scheduler handler manipulation
Verification of scheduler assignment

Implementation Analysis

The testing approach employs a minimalist design using JUnit without Robolectric dependency, demonstrating clean isolation of plugin functionality. The implementation uses EmptyScheduler as a test double and leverages direct assertion validation.

Testing patterns include:

Setup/teardown pattern for plugin state management
Direct scheduler replacement verification
Clean test isolation through reset operations

Technical Details

Testing tools and configuration:

JUnit test framework
EmptyScheduler test utility
RxAndroidPlugins manipulation
AndroidSchedulers main thread access
Assert methods for validation

Best Practices Demonstrated

The test suite exemplifies several testing best practices including proper test isolation, clear setup/teardown procedures, and focused test cases. The code demonstrates:

Clean test state management
Single responsibility principle in test methods
Clear assertion patterns
Efficient test double usage

reactivex/rxandroid

rxandroid/src/test/java/io/reactivex/rxjava3/android/plugins/RxAndroidPluginsNoRobolectricTest.java

            
package io.reactivex.rxjava3.android.plugins;

import io.reactivex.rxjava3.android.schedulers.AndroidSchedulers;
import io.reactivex.rxjava3.android.testutil.EmptyScheduler;
import org.junit.After;
import org.junit.Before;
import org.junit.Test;

import static org.junit.Assert.assertSame;

public final class RxAndroidPluginsNoRobolectricTest {
    @Before @After
    public void setUpAndTearDown() {
        RxAndroidPlugins.reset();
    }
    
    @Test public void mainThreadSchedulerCanBeReplaced() {
        EmptyScheduler emptyScheduler = new EmptyScheduler();
        RxAndroidPlugins.setMainThreadSchedulerHandler(scheduler -> emptyScheduler);
        assertSame(emptyScheduler, AndroidSchedulers.mainThread());
    }
}