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feat(test): add new MultipleAttemptRule, StdOutCaptureRule & StdErrCaptureRule JUnit 4 rules (#327)
* feat(test): add new MultipleAttemptRule JUnit 4 rule * feat(test): add new StdOutCaptureRule & StdErrCaptureRule JUnit 4 rule * fix: line separator failures from windows
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‎java-core/google-cloud-core/src/test/java/com/google/cloud/testing/junit4/MultipleAttemptsRule.java‎

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/*
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* Copyright 2020 Google LLC
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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package com.google.cloud.testing.junit4;
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import static com.google.common.base.Preconditions.checkArgument;
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import java.util.ArrayList;
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import java.util.List;
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import org.junit.rules.TestRule;
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import org.junit.runner.Description;
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import org.junit.runners.model.MultipleFailureException;
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import org.junit.runners.model.Statement;
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/**
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* A JUnit rule that allows multiple attempts of a test execution before ultimately reporting
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* failure for the test. Attempts will be attempted with an exponential backoff which defaults to a
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* starting duration of 1 second.
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*
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* <p>If after the maximum number of attempts the test has still not succeeded, all failures will be
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* propagated as the result of the test allowing all errors to be visible (regardless if they are
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* the same failure or different ones).
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*
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* <p>To use this rule add the field declaration to your JUnit 4 Test class:
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*
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* <p><i>Note: It is important that the field is public</i>
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*
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* <pre>{@code
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* @Rule
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* public MultipleAttemptsRule multipleAttemptsRule = new MultipleAttemptsRule(3);
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* }</pre>
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*
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* @see org.junit.Rule
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*/
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public final class MultipleAttemptsRule implements TestRule {
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private final long initialBackoffMillis;
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private final int maxAttemptCount;
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/**
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* Construct a {@link MultipleAttemptsRule} which will attempt a test up to {@code attemptCount}
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* times before ultimately reporting failure of the test.
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*
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* <p>The initialBackoffMillis will be set to 1000L.
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*
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* @param maxAttemptCount max number of attempts before reporting failure, must be greater than 0
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* @see #MultipleAttemptsRule(int, long)
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*/
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public MultipleAttemptsRule(int maxAttemptCount) {
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this(maxAttemptCount, 1000L);
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}
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/**
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* Construct a {@link MultipleAttemptsRule} which will attempt a test up to {@code attemptCount}
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* times before ultimately reporting failure of the test.
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*
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* <p>The {@code initialBackoffMillis} will be used as the first pause duration before
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* reattempting the test.
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*
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* @param maxAttemptCount max number of attempts before reporting failure, must be greater than 0
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* @param initialBackoffMillis initial duration in millis to wait between attempts, must be
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* greater than or equal to 0
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*/
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public MultipleAttemptsRule(int maxAttemptCount, long initialBackoffMillis) {
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checkArgument(maxAttemptCount > 0, "attemptCount must be > 0");
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checkArgument(initialBackoffMillis >= 0, "initialBackoffMillis must be >= 0");
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this.initialBackoffMillis = initialBackoffMillis;
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this.maxAttemptCount = maxAttemptCount;
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}
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@Override
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public Statement apply(final Statement base, Description description) {
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return new Statement() {
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@Override
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public void evaluate() throws Throwable {
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List<Throwable> failures = new ArrayList<>();
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long retryIntervalMillis = initialBackoffMillis;
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for (int i = 1; i <= maxAttemptCount; i++) {
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try {
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base.evaluate();
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return;
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} catch (Throwable t) {
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failures.add(t);
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Thread.sleep(retryIntervalMillis);
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retryIntervalMillis *= 1.5f;
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}
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}
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MultipleFailureException.assertEmpty(failures);
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}
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};
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}
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}

‎java-core/google-cloud-core/src/test/java/com/google/cloud/testing/junit4/StdErrCaptureRule.java‎

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/*
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* Copyright 2020 Google LLC
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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package com.google.cloud.testing.junit4;
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import java.io.PrintStream;
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import org.junit.Rule;
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/**
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* A JUnit rule that allows the capturing stderr (i.e. {@link System#err} during the scope of a
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* test.
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*
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* <p><i>Note: If some part of the system holds a reference System.err before this rule is loaded
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* into the test lifecycle there is no way for this rule to capture the output. Ensure this rule is
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* declared as high in your test file as possible, and ordered using {@link Rule#order()} before
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* other Rules if necessary.</i>
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*
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* <p>To use this rule add the field declaration to your JUnit 4 Test class:
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*
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* <p><i>Note: It is important that the field is public</i>
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*
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* <pre>{@code
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* @Rule
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* public StdErrCaptureRule stdErrCaptureRule = new StdErrCaptureRule();
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* }</pre>
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*
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* @see org.junit.Rule
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* @see Rule#order()
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*/
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public final class StdErrCaptureRule extends StdXCaptureRule {
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public StdErrCaptureRule() {}
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@Override
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protected PrintStream getOriginal() {
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return System.err;
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}
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@Override
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protected void set(PrintStream ps) {
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System.setErr(ps);
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}
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}

‎java-core/google-cloud-core/src/test/java/com/google/cloud/testing/junit4/StdOutCaptureRule.java‎

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/*
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* Copyright 2020 Google LLC
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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package com.google.cloud.testing.junit4;
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import java.io.PrintStream;
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import org.junit.Rule;
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/**
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* A JUnit rule that allows the capturing stdout (i.e. {@link System#out} during the scope of a
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* test.
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*
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* <p><i>Note: If some part of the system holds a reference System.out before this rule is loaded
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* into the test lifecycle there is no way for this rule to capture the output. Ensure this rule is
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* declared as high in your test file as possible, and ordered using {@link Rule#order()} before
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* other Rules if necessary.</i>
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*
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* <p>To use this rule add the field declaration to your JUnit 4 Test class:
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*
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* <p><i>Note: It is important that the field is public</i>
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*
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* <pre>{@code
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* @Rule
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* public StdOutCaptureRule stdOutCaptureRule = new StdOutCaptureRule();
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* }</pre>
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*
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* @see org.junit.Rule
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* @see Rule#order()
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*/
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public final class StdOutCaptureRule extends StdXCaptureRule {
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public StdOutCaptureRule() {}
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@Override
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protected PrintStream getOriginal() {
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return System.out;
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}
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@Override
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protected void set(PrintStream ps) {
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System.setOut(ps);
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}
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}

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