This document describes how to create custom annotations in Java to simulate a simple unit test framework. It defines two annotations - @Test and @TesterInfo. @Test is used to mark test methods and optionally disable them. @TesterInfo stores metadata about test classes. The document also shows how to use reflection to read the annotations and execute the tests, outputting the results.

1. In this tutorial, we will show you how to create two custom annotations – @Test and @TestInfo , to simulate a simple
unit test framework.
P.S This unit test example is inspired by this official Java annotation article.
1. @Test Annotation
This @interface tells Java this is a custom annotation. Later, you can annotate it on method level like
this @Test(enable=false) .
Test.java
packagepackage comcom..mkyongmkyong..testtest..corecore;;
importimport javajava..langlang..annotationannotation..ElementTypeElementType;;
importimport javajava..langlang..annotationannotation..RetentionRetention;;
importimport javajava..langlang..annotationannotation..RetentionPolicyRetentionPolicy;;
importimport javajava..langlang..annotationannotation..TargetTarget;;
@Retention@Retention((RetentionPolicyRetentionPolicy..RUNTIMERUNTIME))
@Target@Target((ElementTypeElementType..METHODMETHOD)) //can use in method only.//can use in method only.
publicpublic @@interfaceinterface TestTest {{
//should ignore this test?//should ignore this test?
publicpublic booleanboolean enabledenabled(()) defaultdefault truetrue;;
}}
Note
Method declarations must not have any parameters or a throws clause. Return types are restricted to primitives,
String, Class, enums, annotations, and arrays of the preceding types.
2. @TesterInfo Annotation
This @TesterInfo is applied on class level, store the tester details. This shows the different use of return types – enum,
array and string.
TesterInfo.java
packagepackage comcom..mkyongmkyong..testtest..corecore;;
importimport javajava..langlang..annotationannotation..ElementTypeElementType;;
importimport javajava..langlang..annotationannotation..RetentionRetention;;
importimport javajava..langlang..annotationannotation..RetentionPolicyRetentionPolicy;;
importimport javajava..langlang..annotationannotation..TargetTarget;;
@Retention@Retention((RetentionPolicyRetentionPolicy..RUNTIMERUNTIME))
@Target@Target((ElementTypeElementType..TYPETYPE)) //on class level//on class level
publicpublic @@interfaceinterface TesterInfoTesterInfo {{

2. publicpublic enumenum PriorityPriority {{
LOWLOW,, MEDIUMMEDIUM,, HIGHHIGH
}}
PriorityPriority prioritypriority(()) defaultdefault PriorityPriority..MEDIUMMEDIUM;;
StringString[[]] tagstags(()) defaultdefault """";;
StringString createdBycreatedBy(()) defaultdefault "Mkyong""Mkyong";;
StringString lastModifiedlastModified(()) defaultdefault "03/01/2014""03/01/2014";;
}}
3. Unit Test Example
Create a simple unit test example, and annotated with the new custom annotations – @Test and @TesterInfo .
TestExample.java
packagepackage comcom..mkyongmkyong..testtest;;
importimport comcom..mkyongmkyong..testtest..corecore..TestTest;;
importimport comcom..mkyongmkyong..testtest..corecore..TesterInfoTesterInfo;;
importimport comcom..mkyongmkyong..testtest..corecore..TesterInfoTesterInfo..PriorityPriority;;
@TesterInfo@TesterInfo((
prioritypriority == PriorityPriority..HIGHHIGH,,
createdBycreatedBy == "mkyong.com""mkyong.com",,
tagstags == {{"sales""sales",,"test""test" }}
))
publicpublic classclass TestExampleTestExample {{
@Test@Test
voidvoid testAtestA(()) {{
ifif ((truetrue))
throwthrow newnew RuntimeExceptionRuntimeException(("This test always failed""This test always failed"));;
}}
@Test@Test((enabledenabled == falsefalse))
voidvoid testBtestB(()) {{
ifif ((falsefalse))
throwthrow newnew RuntimeExceptionRuntimeException(("This test always passed""This test always passed"));;
}}
@Test@Test((enabledenabled == truetrue))
voidvoid testCtestC(()) {{
ifif ((1010 >> 11)) {{
// do nothing, this test always passed.// do nothing, this test always passed.
}}
}}
}}
4. Java reflection – Read the Annotation
Below example show you how to use Java reflection APIs to read and process the custom annotations.
RunTest.java
packagepackage comcom..mkyongmkyong..testtest;;

3. p g y g ;
importimport javajava..langlang..annotationannotation..AnnotationAnnotation;;
importimport javajava..langlang..reflectreflect..MethodMethod;;
importimport comcom..mkyongmkyong..testtest..corecore..TestTest;;
importimport comcom..mkyongmkyong..testtest..corecore..TesterInfoTesterInfo;;
publicpublic classclass RunTestRunTest {{
publicpublic staticstatic voidvoid mainmain((StringString[[]] argsargs)) throwsthrows ExceptionException {{
SystemSystem..outout..printlnprintln(("Testing...""Testing..."));;
intint passedpassed == 00,, failedfailed == 00,, countcount == 00,, ignoreignore == 00;;
ClassClass<<TestExampleTestExample>> objobj == TestExampleTestExample..classclass;;
// Process @TesterInfo// Process @TesterInfo
ifif ((objobj..isAnnotationPresentisAnnotationPresent((TesterInfoTesterInfo..classclass)))) {{
Annotation annotationAnnotation annotation == objobj..getAnnotationgetAnnotation((TesterInfoTesterInfo..classclass));;
TesterInfo testerInfoTesterInfo testerInfo == ((TesterInfoTesterInfo)) annotationannotation;;
SystemSystem..outout..printfprintf(("%nPriority :%s""%nPriority :%s",, testerInfotesterInfo..prioritypriority(())));;
SystemSystem..outout..printfprintf(("%nCreatedBy :%s""%nCreatedBy :%s",, testerInfotesterInfo..createdBycreatedBy(())));;
SystemSystem..outout..printfprintf(("%nTags :""%nTags :"));;
intint tagLengthtagLength == testerInfotesterInfo..tagstags(())..lengthlength;;
forfor ((String tagString tag :: testerInfotesterInfo..tagstags(()))) {{
ifif ((tagLengthtagLength >> 11)) {{
SystemSystem..outout..printprint((tagtag ++ ", "", "));;
}} elseelse {{
SystemSystem..outout..printprint((tagtag));;
}}
tagLengthtagLength----;;
}}
SystemSystem..outout..printfprintf(("%nLastModified :%s%n%n""%nLastModified :%s%n%n",, testerInfotesterInfo..lastModifiedlastModified(())));;
}}
// Process @Test// Process @Test
forfor ((Method methodMethod method :: objobj..getDeclaredMethodsgetDeclaredMethods(()))) {{
// if method is annotated with @Test// if method is annotated with @Test
ifif ((methodmethod..isAnnotationPresentisAnnotationPresent((TestTest..classclass)))) {{
Annotation annotationAnnotation annotation == methodmethod..getAnnotationgetAnnotation((TestTest..classclass));;
Test testTest test == ((TestTest)) annotationannotation;;
// if enabled = true (default)// if enabled = true (default)
ifif ((testtest..enabledenabled(()))) {{
trytry {{
methodmethod..invokeinvoke((objobj..newInstancenewInstance(())));;
SystemSystem..outout..printfprintf(("%s - Test '%s' - passed %n""%s - Test '%s' - passed %n",, ++++countcount,, methodmethod..getNamegetName(())));;
passedpassed++++;;
}} catchcatch ((ThrowableThrowable exex)) {{
SystemSystem..outout..printfprintf(("%s - Test '%s' - failed: %s %n""%s - Test '%s' - failed: %s %n",, ++++countcount,, methodmethod..getNamegetName(()),, exex..getCausegetCause(())));;
failedfailed++++;;
}}
}} elseelse {{
SystemSystem..outout..printfprintf(("%s - Test '%s' - ignored%n""%s - Test '%s' - ignored%n",, ++++countcount,, methodmethod..getNamegetName(())));;
ignoreignore++++;;
}}

4. }}
}}
}}
SystemSystem..outout..printfprintf(("%nResult : Total : %d, Passed: %d, Failed %d, Ignore %d%n""%nResult : Total : %d, Passed: %d, Failed %d, Ignore %d%n",, countcount,, passedpassed,, failedfailed,, ignoreignore));;
}}
}}
Output
TestingTesting......
Priority :HIGHPriority :HIGH
CreatedBy :mkyong.comCreatedBy :mkyong.com
Tags :sales,Tags :sales, testtest
LastModified :03/01/2014LastModified :03/01/2014
1 - Test1 - Test 'testA''testA' - failed: java.lang.RuntimeException: This- failed: java.lang.RuntimeException: This testtest always failedalways failed
2 - Test2 - Test 'testC''testC' - passed- passed
3 - Test3 - Test 'testB''testB' - ignored- ignored
ResultResult :: TotalTotal :: 3, Passed: 1, Failed 1, Ignore 13, Passed: 1, Failed 1, Ignore 1