ru.vyarus.dropwizard.guice.test.StartupErrorRule Maven / Gradle / Ivy
package ru.vyarus.dropwizard.guice.test;
import org.junit.contrib.java.lang.system.ExpectedSystemExit;
import org.junit.contrib.java.lang.system.SystemErrRule;
import org.junit.contrib.java.lang.system.SystemOutRule;
import org.junit.contrib.java.lang.system.internal.CheckExitCalled;
import org.junit.rules.TestRule;
import org.junit.runner.Description;
import org.junit.runners.model.Statement;
/**
* Dropwizard exit with code 1 in case of exception during command run. In order to test error situations
* system exit must be prevented.
* Rule use system rules to intercept
* exit and output streams (system.out, system.err).
*
* Extra dependency 'com.github.stefanbirkner:system-rules:1.16.0' is required.
*
* In spock tests, 'then' section must contain {@code rule.indicatorExceptionType} (or {@code thrown(CheckExitCalled)})
* as rule can't intercept this exception.
* 'then' section can be used for assertions after system exit and so no need to register custom callback in the rule.
*
* For Junit 5 there is no direct alternative, but there are options:
*
* - For system exit capturing you can use https://github.com/tginsberg/junit5-system-exit
* - For system streams capturing there is no alternatives, but in any case it is impossible to do for parallel
* tests
*
*
* @author Vyacheslav Rusakov
* @since 16.03.2017
*/
public final class StartupErrorRule implements TestRule {
private final ExpectedSystemExit exit = ExpectedSystemExit.none();
private final SystemErrRule systemErr = new SystemErrRule();
private final SystemOutRule systemOut = new SystemOutRule();
private StartupErrorRule() {
exit.expectSystemExitWithStatus(1);
systemErr.enableLog();
systemOut.enableLog();
}
/**
* Use with spock tests or when no assertions required after system exit call.
*
* @return rule instance
*/
public static StartupErrorRule create() {
return new StartupErrorRule();
}
/**
* This is useful for junit tests, because there is no other way to check anything after exit call.
* In spock, 'then' section is always called and so may be used for assertions.
*
* @param check assertion callback to execute after exit call
* @return activated rule
*/
public static StartupErrorRule create(final AfterExitAssertion check) {
return create().checkAfterExit(check);
}
/**
* In junit it is impossible to use assertion lines after {@code System.exit()} call. This method will register
* a custom check callback to validate state after system exit call.
* May be called multiple times.
*
* NOTE: in spock there is no need for it, because 'then' section will be called.
*
* @param check assertion command
* @return rule instance for chained calls
* @see ExpectedSystemExit#checkAssertionAfterwards(org.junit.contrib.java.lang.system.Assertion)
*/
public StartupErrorRule checkAfterExit(final AfterExitAssertion check) {
exit.checkAssertionAfterwards(() -> check.check(getOutput(), getError()));
return this;
}
@Override
public Statement apply(final Statement base, final Description description) {
// sys.out -> sys.err -> system exit
return systemOut.apply(
systemErr.apply(
exit.apply(base, description),
description),
description);
}
/**
* NOTE: useful only for spock tests.
*
* @return content of system.out or empty string
*/
public String getOutput() {
return clearString(systemOut.getLog());
}
/**
* Dropwizard exception will be presented here.
*
* NOTE: useful only for spock tests.
*
* @return content of system.err or empty string
*/
public String getError() {
return clearString(systemErr.getLog());
}
/**
* Useful only for spock tests because in junit rule can intercept this exception implicitly.
*
* @return type of exception thrown when exit called
*/
public Class getIndicatorExceptionType() {
return CheckExitCalled.class;
}
private String clearString(final String message) {
return message.trim().replaceAll("\r", "");
}
/**
* Interface implementation may be registered to check assertions after system exit.
*/
@FunctionalInterface
public interface AfterExitAssertion {
/**
* Called after system exit call to perform custom assertions.
*
* @param out output stream content or empty string
* @param err error stream content (exception logged there)
* @throws Exception in case of error
*/
void check(String out, String err) throws Exception;
}
}