Testing with Thread.sleep

Question

What are the recommended approaches to using Thread.sleep() to speed up tests.

I am testing a network library with a retry functionality when connection

Answer 1

Create some retry delay type that represents the policy for retry delays. Invoke some method on the policy type for the delay. Mock it as you like. No conditional logic, or true/false flags. Just inject the type that you want.

In ConnectRetryPolicy.java

public interface ConnectRetryPolicy {
    void doRetryDelay();
}

In SleepConnectRetryPolicy.java

public class final SleepConnectRetryPolicy implements ConnectRetryPolicy {
    private final int delay;
    public SleepConnectRetryPolicy(final int delay) {
        this.delay = delay;
    }

    @Override
    public void doRetryDelay() {
        try {
            Thread.sleep(delay);
        } catch (InterruptedException ie) {
            log.error("connection delay sleep interrupted", ie);
        }
    }
}

In MockConnectRetryPolicy.java

public final class MockConnectRetryPolicy implements ConnectRetryPolicy {    
    @Override
    public void doRetryDelay() {
        // no delay
    }
}