de.weltraumschaf.commons.testing

Class CapturedOutput

java.lang.Object

de.weltraumschaf.commons.testing.CapturedOutput

All Implemented Interfaces:

org.junit.rules.TestRule

public final class CapturedOutput
extends Object
implements org.junit.rules.TestRule

This rule captures all output written to System.out and System.err.

This rule redirects the constant print streams for out/err to an CapturingPrintStream before each test and backups the origin streams after each test.

public class OutputTest {

     @Rule
     public final CapturedOutput output = new CapturedOutput();

     @Test
     public void captureOut() {
         output.expectOut("foobar");
         output.expectOut(not("snafu"));

         System.out.print("foobar");
     }

     @Test
     public void captureErr() {
         output.expectErr("foobar");
         output.expectErr(not("snafu"));

         System.err.print("foobar");
     }

 }
 

Since:

1.0.0

Author:

Sven Strittmatter

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
private static class	CapturedOutput.CapturedOutputMatcherBuilder Builds string matchers.

Field Summary

Fields

Modifier and Type	Field and Description
private CapturingPrintStream	err Captures the data written to STDERR.
private PrintStream	errBackup Holds the original STDERR from before test method.
private CapturedOutput.CapturedOutputMatcherBuilder	errMatcherBuilder Build the matchers for STDERR expectations.
private CapturingPrintStream	out Captures the data written to STDOUT.
private PrintStream	outBackup Holds the original STDOUT from before test method.
private CapturedOutput.CapturedOutputMatcherBuilder	outMatcherBuilder Build the matchers for STDOUT expectations.

Constructor Summary

Constructors

Constructor and Description
CapturedOutput() Creates a capturing rule with platform encoding.
CapturedOutput(String encoding) Dedicated constructor.

Method Summary

Methods

Modifier and Type	Method and Description
org.junit.runners.model.Statement	apply(org.junit.runners.model.Statement base, Description description)
private void	assertCapturedErr() Applies matchers on captured error output if there are any matchers.
private void	assertCapturedOut() Applies matchers on captured standard output if there are any matchers.
void	expectErr(org.hamcrest.Matcher<String> matcher) Adds to the list of requirements for any output printed to STDERR.
void	expectErr(String substring) Adds to the list of requirements for any output printed to STDERR that it should contain string substring.
void	expectOut(org.hamcrest.Matcher<String> matcher) Adds to the list of requirements for any output printed to STDOUT.
void	expectOut(String substring) Adds to the list of requirements for any output printed to STDOUT that it should contain string substring.
private static <T> T	notNull(T subject, String description) Validates that given subject is not null.
private void	redirectOutputStreams() Set and backup STDERR/STDOUT print streams.
private void	restoreOutputStreams() Restore STDERR/STDOUT print streams.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

outMatcherBuilder

private final CapturedOutput.CapturedOutputMatcherBuilder outMatcherBuilder

Build the matchers for STDOUT expectations.

errMatcherBuilder

private final CapturedOutput.CapturedOutputMatcherBuilder errMatcherBuilder

Build the matchers for STDERR expectations.

out

private final CapturingPrintStream out

Captures the data written to STDOUT.

err

private final CapturingPrintStream err

Captures the data written to STDERR.

outBackup

private PrintStream outBackup

Holds the original STDOUT from before test method.

errBackup

private PrintStream errBackup

Holds the original STDERR from before test method.

Constructor Detail

CapturedOutput

public CapturedOutput()
               throws UnsupportedEncodingException

Creates a capturing rule with platform encoding.

Throws:

UnsupportedEncodingException - if the platform encoding is not supported

CapturedOutput

public CapturedOutput(String encoding)
               throws UnsupportedEncodingException

Dedicated constructor.

Parameters:

encoding - must not be null or empty

Throws:

UnsupportedEncodingException - if the platform encoding is not supported

Method Detail

expectOut

public void expectOut(String substring)

Adds to the list of requirements for any output printed to STDOUT that it should contain string substring.

Parameters:

substring - must not be null

expectOut

public void expectOut(org.hamcrest.Matcher<String> matcher)

Adds to the list of requirements for any output printed to STDOUT.

Parameters:

matcher - must not be null

expectErr

public void expectErr(String substring)

Adds to the list of requirements for any output printed to STDERR that it should contain string substring.

Parameters:

substring - must not be null

expectErr

public void expectErr(org.hamcrest.Matcher<String> matcher)

Adds to the list of requirements for any output printed to STDERR.

Parameters:

matcher - must not be null

apply

public org.junit.runners.model.Statement apply(org.junit.runners.model.Statement base,
                                      Description description)

Specified by:

apply in interface org.junit.rules.TestRule

redirectOutputStreams

private void redirectOutputStreams()

Set and backup STDERR/STDOUT print streams.

assertCapturedErr

private void assertCapturedErr()
                        throws UnsupportedEncodingException

Applies matchers on captured error output if there are any matchers.

Throws:

UnsupportedEncodingException - if the platform encoding is not supported

assertCapturedOut

private void assertCapturedOut()
                        throws UnsupportedEncodingException

Applies matchers on captured standard output if there are any matchers.

Throws:

UnsupportedEncodingException - if the platform encoding is not supported

restoreOutputStreams

private void restoreOutputStreams()

Restore STDERR/STDOUT print streams.

notNull

private static <T> T notNull(T subject,
            String description)

Validates that given subject is not null.

Will throw NullPointerException if subject is null.

Type Parameters:

T - type of subject

Parameters:

subject - tested subject

description - name of tested subject for exception message

Returns:

the subject, if not null