log

README.md

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+# SLF4JTesting
+
+SLF4TTesting provides a "Testing Double" of SLF4J LoggerFactory to facilitate log testing but also as a utility
+for use in unit and integration tests to conveniently configure logging on a test by test basis.
+
+SLF4TTesting has been designed to:
+
+- support unit and integration testing
+- support concurrent test execution such as [TestNG parallel suites](http://testng.org/doc/documentation-main.html#parallel-suites) or [Scalatest parallel test execution](http://doc.scalatest.org/2.0/index.html#org.scalatest.ParallelTestExecution) 
+- promote dependency injection of the logging implementation
+- support testing of multi-threaded components
+- support testing of assemblies
+- provide a simple console logging facility
+- allow selective suppression of individual console logging messages (eg to hide any expected errors)
+- support integration with mocking libraries (eg Mockito)
+
+SLT4FTesting differs from some other solutions because it:   
+
+* does not pollute the classpath with any StaticLoggerBinder stuff
+* does not compete with other SLF4J implementations resident on the classpath
+* does not rely on cluttering the classpath with special logback.xml/logback-test.xml files
+* does not use statics
+* does not rely on singletons anywhere
+* does not need thread-locals etc 
+
+## Usage
+
+### Setting up
+
+Include the jar as a test dependency.
+
+### Basic Example
+
+Here we use constructor injection using the SLF4J logger factory interface.
+
+```java
+import org.slf4j.ILoggerFactory;
+import org.slf4j.Logger;
+
+public class Example1 {
+
+    private final Logger logger;
+
+    public Example1(ILoggerFactory lf) {
+        this.logger = lf.getLogger(Example1.class.getName());
+    }
+
+    public void aMethodThatLogs() {
+        logger.info("Hello World!");
+    }
+}
+```
+
+The `.getName()` is a tiny bit of boilerplate that's only necessary because SLF4J's'
+(ILoggerFactory)[http://www.slf4j.org/api/org/slf4j/ILoggerFactory.html] interface does not provide a by-class convenience
+method like (LoggerFactory)[http://www.slf4j.org/api/org/slf4j/LoggerFactory.html] does.
+
+Constructor injection is not that arduous, even less so if you use a dependecy injection framework, but it provides the seam that allows us to
+inject out testing double.
+
+```java
+import org.junit.Test;
+import static org.junit.Assert.assertTrue;
+
+public class Example1UnitTest {
+
+    @Test
+    public void testAMethodThatLogs() throws Exception {
+        TestLoggerFactory loggerFactory = new TestLoggerFactory();
+
+        Example1 sut = new Example1(loggerFactory);
+        sut.aMethodThatLogs();
+
+        TestLogger logger = loggerFactory.getLogger(Example1.class.getName());
+        assertTrue(logger.contains(".*Hello.*"));
+    }
+}
+```
+
+
+## Motivation
+
+### Improved construction patterns and testability
+
+I strongly believe in dependency injection (DI) so anything that looks like a static or singleton offends me,
+statics and singletons are an impediment to testable code.
+
+We can't conveniently substitute statics for during testing and in the case of SLF4J we end up resorting to
+nasties like classpath manipulation to get over this.
+
+Anything global or static leaks information between tests and typically requires before and after setup
+and tear down which is more test boilerplate.
+This pattern means that running tests classes or class methods concurrently leads to interference as all threads interact with the
+shared mutable global.
+
+These problems can be avoided if we do not permit this share state between tests and instead use POJO's and DI; this library attempts
+to make it easy to use a POJO/DI pattern with SLF4J and write tests for that code.
+
+### Console logging during tests
+
+Typically we don't want logging going to the console in tests. A possible exception to this is that it's useful
+if any unexpected errors are logged to the console. Sometimes however we are performing negative tests and we expect
+certain error messages but we do not want to see these on the console.
+
+SLF4JTesting supports optional console logging but also a regex based scheme to suppress certain expected log lines.
+This helps us keep our CI console clean without losing the benefits of logging of unexpected conditions that would help
+us diagnose failing tests more easily.
+
+### Multithreaded code
+
+Sometimes we have an integration test where the test subject performs logging from another thread than the foreground test thread.
+SLF4JTesting collects all logging occurring in the test subject regardless of thread.
+
+### Assembly integration testing
+
+Sometimes we want to test an assembly where the assembly constructs objects internally.
+If each parent object is injected with the logger factory and any objects the parent creates are also injected with the
+ logger factory then this pattern allows the entire logging implementation to be substituted in tests.
+
+ ```java
+ import org.slf4j.ILoggerFactory;
+ import org.slf4j.Logger;
+
+ public class AssemblyExample {
+
+     private final ChildObject child;
+
+     public AssemblyExample(ILoggerFactory lf) {
+         child = new ChildObject(lf);
+     }
+ }
+
+ class ChildObject {
+     private final Logger logger;
+     private final GrandchildObject grandchild;
+
+     ChildObject(ILoggerFactory lf) {
+         logger = lf.getLogger(AssemblyExample.class.getName());
+         grandchild = new GrandchildObject(lf);
+     }
+
+     public void aMethodThatLogs() {
+         logger.info("Hello World!");
+     }
+ }
+
+ class GrandchildObject {
+     private final Logger logger;
+
+     GrandchildObject (ILoggerFactory lf) {
+         logger = lf.getLogger(AssemblyExample.class.getName());
+     }
+
+     public void aMethodThatLogs() {
+         logger.info("Bye World!");
+     }
+ }
+ ```
+
+### Making assertions
+
+It is possible to make some assertions about what was logged by using methods provided by   TestLogger`.`
+
+```
+TestLogger logger = loggerFactory.getLogger(Example1.class.getName());
+assertTrue(logger.contains(".*Hello.*"));
+```
+
+### Mocking
+
+You can make further assertions by using a mocking framework.
+
+SLF4JLogging allows you to hook a mock (eg Mockito or other) up to the logging implementation so that
+ you can use the power of your chosen mocking framework directly to test the logging.
+
+SLF4J logging does not impose any particular mocking framework.
+
+```java
+public class MockingExampleUnitTest {
+    @Test
+    public void testAMethodThatLogsWithAMock() throws Exception {
+        Logger mockLogger = Mockito.mock(Logger.class);
+
+        Settings cfg = new Settings().delegate(BasicExample.class.getName(), mockLogger);
+        TestLoggerFactory loggerFactory = new TestLoggerFactory(cfg);
+
+        BasicExample sut = new BasicExample(loggerFactory);
+        sut.aMethodThatLogs();
+
+        Mockito.verify(mockLogger).info("Hello World!");
+    }
+}
+```

build.gradle

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+group 'portingle'
+version '0.0-SNAPSHOT'
+
+apply plugin: 'java'
+
+sourceCompatibility = 1.7
+
+repositories {
+    mavenCentral()
+}
+
+dependencies {
+    compile 'org.slf4j:slf4j-api:1.7.5'
+
+    testCompile 'junit:junit:4.11'
+    testCompile 'org.mockito:mockito-all:1.10.19'
+
+
+}

gradle/wrapper/gradle-wrapper.properties

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+#Wed Dec 02 23:12:13 GMT 2015
+distributionBase=GRADLE_USER_HOME
+distributionPath=wrapper/dists
+zipStoreBase=GRADLE_USER_HOME
+zipStorePath=wrapper/dists
+distributionUrl=https\://services.gradle.org/distributions/gradle-2.9-bin.zip

gradlew

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+#!/usr/bin/env bash
+
+##############################################################################
+##
+##  Gradle start up script for UN*X
+##
+##############################################################################
+
+# Add default JVM options here. You can also use JAVA_OPTS and GRADLE_OPTS to pass JVM options to this script.
+DEFAULT_JVM_OPTS=""
+
+APP_NAME="Gradle"
+APP_BASE_NAME=`basename "$0"`
+
+# Use the maximum available, or set MAX_FD != -1 to use that value.
+MAX_FD="maximum"
+
+warn ( ) {
+    echo "$*"
+}
+
+die ( ) {
+    echo
+    echo "$*"
+    echo
+    exit 1
+}
+
+# OS specific support (must be 'true' or 'false').
+cygwin=false
+msys=false
+darwin=false
+case "`uname`" in
+  CYGWIN* )
+    cygwin=true
+    ;;
+  Darwin* )
+    darwin=true
+    ;;
+  MINGW* )
+    msys=true
+    ;;
+esac
+
+# Attempt to set APP_HOME
+# Resolve links: $0 may be a link
+PRG="$0"
+# Need this for relative symlinks.
+while [ -h "$PRG" ] ; do
+    ls=`ls -ld "$PRG"`
+    link=`expr "$ls" : '.*-> \(.*\)$'`
+    if expr "$link" : '/.*' > /dev/null; then
+        PRG="$link"
+    else
+        PRG=`dirname "$PRG"`"/$link"
+    fi
+done
+SAVED="`pwd`"
+cd "`dirname \"$PRG\"`/" >/dev/null
+APP_HOME="`pwd -P`"
+cd "$SAVED" >/dev/null
+
+CLASSPATH=$APP_HOME/gradle/wrapper/gradle-wrapper.jar
+
+# Determine the Java command to use to start the JVM.
+if [ -n "$JAVA_HOME" ] ; then
+    if [ -x "$JAVA_HOME/jre/sh/java" ] ; then
+        # IBM's JDK on AIX uses strange locations for the executables
+        JAVACMD="$JAVA_HOME/jre/sh/java"
+    else
+        JAVACMD="$JAVA_HOME/bin/java"
+    fi
+    if [ ! -x "$JAVACMD" ] ; then
+        die "ERROR: JAVA_HOME is set to an invalid directory: $JAVA_HOME
+
+Please set the JAVA_HOME variable in your environment to match the
+location of your Java installation."
+    fi
+else
+    JAVACMD="java"
+    which java >/dev/null 2>&1 || die "ERROR: JAVA_HOME is not set and no 'java' command could be found in your PATH.
+
+Please set the JAVA_HOME variable in your environment to match the
+location of your Java installation."
+fi
+
+# Increase the maximum file descriptors if we can.
+if [ "$cygwin" = "false" -a "$darwin" = "false" ] ; then
+    MAX_FD_LIMIT=`ulimit -H -n`
+    if [ $? -eq 0 ] ; then
+        if [ "$MAX_FD" = "maximum" -o "$MAX_FD" = "max" ] ; then
+            MAX_FD="$MAX_FD_LIMIT"
+        fi
+        ulimit -n $MAX_FD
+        if [ $? -ne 0 ] ; then
+            warn "Could not set maximum file descriptor limit: $MAX_FD"
+        fi
+    else
+        warn "Could not query maximum file descriptor limit: $MAX_FD_LIMIT"
+    fi
+fi
+
+# For Darwin, add options to specify how the application appears in the dock
+if $darwin; then
+    GRADLE_OPTS="$GRADLE_OPTS \"-Xdock:code=$APP_NAME\" \"-Xdock:icon=$APP_HOME/media/gradle.icns\""
+fi
+
+# For Cygwin, switch paths to Windows format before running java
+if $cygwin ; then
+    APP_HOME=`cygpath --path --mixed "$APP_HOME"`
+    CLASSPATH=`cygpath --path --mixed "$CLASSPATH"`
+    JAVACMD=`cygpath --unix "$JAVACMD"`
+
+    # We build the pattern for arguments to be converted via cygpath
+    ROOTDIRSRAW=`find -L / -maxdepth 1 -mindepth 1 -type d 2>/dev/null`
+    SEP=""
+    for dir in $ROOTDIRSRAW ; do
+        ROOTDIRS="$ROOTDIRS$SEP$dir"
+        SEP="|"
+    done
+    OURCYGPATTERN="(^($ROOTDIRS))"
+    # Add a user-defined pattern to the cygpath arguments
+    if [ "$GRADLE_CYGPATTERN" != "" ] ; then
+        OURCYGPATTERN="$OURCYGPATTERN|($GRADLE_CYGPATTERN)"
+    fi
+    # Now convert the arguments - kludge to limit ourselves to /bin/sh
+    i=0
+    for arg in "$@" ; do
+        CHECK=`echo "$arg"|egrep -c "$OURCYGPATTERN" -`
+        CHECK2=`echo "$arg"|egrep -c "^-"`                                 ### Determine if an option
+
+        if [ $CHECK -ne 0 ] && [ $CHECK2 -eq 0 ] ; then                    ### Added a condition
+            eval `echo args$i`=`cygpath --path --ignore --mixed "$arg"`
+        else
+            eval `echo args$i`="\"$arg\""
+        fi
+        i=$((i+1))
+    done
+    case $i in
+        (0) set -- ;;
+        (1) set -- "$args0" ;;
+        (2) set -- "$args0" "$args1" ;;
+        (3) set -- "$args0" "$args1" "$args2" ;;
+        (4) set -- "$args0" "$args1" "$args2" "$args3" ;;
+        (5) set -- "$args0" "$args1" "$args2" "$args3" "$args4" ;;
+        (6) set -- "$args0" "$args1" "$args2" "$args3" "$args4" "$args5" ;;
+        (7) set -- "$args0" "$args1" "$args2" "$args3" "$args4" "$args5" "$args6" ;;
+        (8) set -- "$args0" "$args1" "$args2" "$args3" "$args4" "$args5" "$args6" "$args7" ;;
+        (9) set -- "$args0" "$args1" "$args2" "$args3" "$args4" "$args5" "$args6" "$args7" "$args8" ;;
+    esac
+fi
+
+# Split up the JVM_OPTS And GRADLE_OPTS values into an array, following the shell quoting and substitution rules
+function splitJvmOpts() {
+    JVM_OPTS=("$@")
+}
+eval splitJvmOpts $DEFAULT_JVM_OPTS $JAVA_OPTS $GRADLE_OPTS
+JVM_OPTS[${#JVM_OPTS[*]}]="-Dorg.gradle.appname=$APP_BASE_NAME"
+
+exec "$JAVACMD" "${JVM_OPTS[@]}" -classpath "$CLASSPATH" org.gradle.wrapper.GradleWrapperMain "$@"