Unit Testing at Scale

Unit Testing
at Scale
Jan Wloka
jan.wloka@quatico.com
Quatico Solutions AG

Text Image Component
JSP Template
class
TextImageItem
class
TextImageController
<creates>
<creates>
<uses>
<uses>
3

Text Image Component
MVC
JSP Template
class
TextImageItem
class
TextImageController
<creates>
<creates>
<uses>
<uses>
3

Testing Text Image Component
AEM
Resources
App
TextImage
TextImage
Test
<creates>
<tests>
4

Test: Image Legend@Test
public void testGetImageLegendWithSourceAndCaptionReturnsBoth() throws Exception {
ResourceResolver resolver = new ResourceResolverImpl(client);
createPage(“/content/foobar”, new Properties(), PageType.PRESENCE.getTemplate());
createPage(“/content/foobar/ko”, new Properties(), PageType.LANGUAGE.getTemplate());
createPage(“/content/foobar/ko/home", new Properties(), PageType.HOME.getTemplate());
createPage(“/content/foobar/ko/home/content", new Properties(), PageType.DETAIL.getTemplate());
Resource contentPage = resolver.getResource(“/content/foobar/ko/home/content");
createResource(contentPage.getPath() + "/jcr:content/textimage", new Properties());
Resource target = resolver.getResource(contentPage.getPath() + "/jcr:content/textimage");
Properties imageProps = new Properties()
.append("source", "<sourceValue>")
.append("caption", "titleValue")
.append("sling:resourceType", ComponentType.IMAGE)
.append(JCR_LASTMODIFIED, new Time().format(DateFormat.GMT))
.append(JCR_LAST_MODIFIED_BY, "admin");
createResource(contentPage.getPath() + "/jcr:content/textimage/image", imageProps);
TextImageController testObj = new TextImageController().setup(createContext(target, contentPage));
assertEquals("titleValue<br /><sourceValue>", testObj.getImageLegend());
}
5

}
Assemble
5

}
Assemble
Act
5

}
Assemble
Act
Assert
5

AEM Sling Testing API
@Before
public void setUp() throws Exception {
URL url = new URL(serverUrl);
httpClient = new HttpClient();
httpClient.getParams().setAuthenticationPreemptive(true);
httpClient.getState().setCredentials(new AuthScope(url.getHost(), url.getPort(), ANY_REALM), getCredentials());
client = new SlingIntegrationTestClient(httpClient);
}
private void createPage(String path, Properties properties, Template template) throws Exception {
String[] pair = splitPathName(path);
HttpMethod createReq = new PostMethod(serverUrl + "/bin/wcmcommand");
createReq.setQueryString(new Properties().append("cmd", “createPage").append("title", pair[1])
.append("parentPath", pair[0]).append(TEMPLATE, template.getName()).toPairs());
if (HttpStatus.SC_OK != httpClient.executeMethod(createReq)) {
throw new HttpResponseException(createReq.getStatusCode(), createReq.getStatusText());
}
if (!properties.isEmpty()) {
HttpMethod changeReq = new PostMethod(serverUrl + path + "/" + JCR_CONTENT);
changeReq.setQueryString(properties.toPairs(true));
if (HttpStatus.SC_OK != httpClient.executeMethod(changeReq)) {
throw new HttpResponseException(changeReq.getStatusCode(), changeReq.getStatusText());
}
}
}
private String createResource(String path, Properties properties) throws IOException {
String nodeUrl = serverUrl + path;
client.createNode(nodeUrl, properties.<String>toMap());
return nodeUrl;
}

@Before
}
}
}
}
}
return nodeUrl;
}
Setup Client

@Before
}
}
}
}
}
return nodeUrl;
}
Create
Page

@Before
}
}
}
}
}
return nodeUrl;
}
Setup Resource

Why do you write tests?
Feedback!
7

Why do you write tests?
Run tests as change detector? Run frequently, run fast!
Feedback!
7

Integrated tests seem great,
at ﬁrst
“When using Java models, a common approach is
to use unit tests to do this, and rely on Mockito or
similar frameworks to simulate the behaviour of the
AEM environment. Within such a rich environment,
however, the test code quickly becomes hard to
follow, as most of it is setting up the AEM
simulation. Worse still, it’s very easy to get the
simulation wrong, meaning your tests pass but
your code is actually buggy.”  
— Jon Barber, In-container testing for AEM projects
8

What it’s missing?
• Integrated tests
✓ Can reproduce a bug
– Run slow, thus infrequently —> delay feedback
– No design feedback
9

What it’s missing?
• Integrated tests
– Run slow, thus infrequently —> delay feedback
– No design feedback
• Isolated tests
✓ Run fast, thus frequently —> immediate feedback
✓ Put pressure on the design —> design feedback!
9

Design  
Feedback vs. Degradation
100%
tests passed; but
bug in Code
Too many
dependencies; write
integrated tests
Slower
feedback = less time
to write tests; more
opportunities for
bugs
Harder
to write unit tests;
write more integrated
tests
No design
feedback; more
sloppy design
Design
Degradation
by J.B. Rainsberger

Object Interactions
Client
Service
Object:c Object:s
11

Object Interactions
Client
Service
Interface
Object:c Object:s
11

Object Interactions
Client
Service
Interface
Do I ask the
correct questions?
Object:c Object:s
11

Object Interactions
Client
Service
Interface
Do I ask the
correct questions?
Can I answer all
questions you’re asking?
Object:c Object:s
11

Object Interactions
Client
Service
Interface
Do I ask the
correct questions?
Can I answer all
Do I handle all responses?
Object:c Object:s
11

Object Interactions
Client
Service
Interface
Do I ask the
correct questions?
Can I answer all
Can I give you the answer
you might think I can?
Object:c Object:s
11

Testing Object Interactions
Interface
Client
Service
Do I ask the
correct questions?
Can I answer all
Object:c Object:s
12

Interface
Client
Service
Does C ask S only
correct questions?
Can I answer all
Object:c Object:s
12

Interface
Client
Service
Does C ask S only
correct questions?
Does S have the
impl. C depends on?
Object:c Object:s
12

Interface
Client
Service
Does C ask S only
correct questions?
Can C handle all
responses of S?
Does S have the
impl. C depends on?
Object:c Object:s
12

Interface
Client
Service
Does C ask S only
correct questions?
Can C handle all
responses of S?
Does S have the
impl. C depends on?
Does S’s impl. responds
in the way C expects?
Object:c Object:s
12

Interface
Client
Service
Does C ask S only
correct questions?
Can C handle all
responses of S?
Does S have the
impl. C depends on?
Does S’s impl. responds
in the way C expects?
Collaboration Test Contract Test
Object:c Object:s
12

Test: Image Legend revisited
# init() : void
+ validate() : Status
+ isShowTitleBelow() : boolean
+ getImageLegend() : String
TextImageController
TextImageItem
+ getHref() : String
+ getFullViewHref() : String
+ getHtml() : String
+ getImageLegend(String) : String
+ caption : String
+ alt : String
+ source : String
+ fullViewMaxWidth : String
+ enableFullView : Boolean
+ imageSize : ImageSize
+ imagePosition : ImagePosition
+ imageData : ImageDataItem
ImageItem
+ title : String
+ text : String
+ isRichText : boolean
Text
+ description : String
+ text : String
+ title : String
+ target : String
+ cssClass : String
+ icon : String
+ active : boolean
+ targetPageIsLinkable : boolean
+ pathRewritingDisabled : boolean
+ escapingDisabled : boolean
+ children : List
+ urlPath : String
+ urlQueryPart : String
Link
+ testValidateWithEmptyTextResourceYieldsWarning()
+ testValidateWithTextResourceYieldsOk()
+ testIsShowTitleBelowWithNoImageIsPresentReturnsFalse()
+ testIsShowTitleBelowWithImageIsPresentAndImageSizeIsSmallAndImagePositionIsLeftReturnFalse()
+ testIsShowTitleBelowWithImageIsPresentAndImageSizeIsNormalAndImagePositionIsRightReturnsFalse()
+ testIsShowTitleBelowWithImageIsPresentAndImageSizeIsSmallAndImagePositionIsRightReturnsFalse()
+ testIsShowTitleBelowWithImageIsPresentAndImageSizeIsNormalAndImagePositionIsLeftReturnsTrue()
+ testGetImageLegendReturnsEmptyWhenNoTitleAndSourceIsSet()
+ testGetImageLegendReturnsSourceWhenOnlySourceIsSet()
+ testGetImageLegendReturnsTitleWhenOnlyTitleIsSet()
+ testGetImageLegendReturnsAppendedTitleAndSource()
TextImageControllerTest
13

Collaboration Tests
• Does client ask service only correct questions?
• Does TextImageItem ask ImageItem only correct
questions?
• Can client handle all possible responses of
service?
• Can TextImageItem handle all possible
responses of ImageItem?
14

Does TextImageItem ask only
correct questions?
15

Does TextImageItem ask only
correct questions?
YES.
15

Can TextImageItem handle all
possible responses?
@Test
public void testGetImageLegendWithNullLegendReturnsEmptyString() throws Exception {
ImageItem target = mock(ImageItem.class);
when(target.getImageLegend(anyString())).thenReturn(null);
TextImageItem testObj = new TextImageItem().setImage(target);
assertEquals(StringUtils.EMPTY, testObj.getImageLegend());
}
@Test
public void testGetImageLegendWithSomeLegendReturnsLegendString() throws Exception {
ImageItem target = mock(ImageItem.class);
when(target.getImageLegend(anyString())).thenReturn("foobar");
TextImageItem testObj = new TextImageItem().setImage(target);
assertEquals("foobar", testObj.getImageLegend());
}
16

Contract Tests
• Does service have the implementation client
depends on?
• Does ImageItem#getImageLegend(String)
have the right implementation?
• Does service’s implementation responds in the
way client expects?
• Does ImageItem#getImageLegend(String)
method responds as expected?
17

Does ImageItem#getImageLegend(String)
have the right implementation?
public void testGetImageLegendWithEmptySeparatorAndDefaultValuesReturnsEmptyString() thro
assertEquals(StringUtils.EMPTY, new ImageItem().getImageLegend("")); 
} 
public void testGetImageLegendWithSomeSeparatorAndDefaultValuesReturnsEmptyString() throw
assertEquals(StringUtils.EMPTY, new ImageItem().getImageLegend("SEP")); 
} 
 
public void testGetImageLegendWithEmptySeparatorAndCaptionAndSourceValueReturnsCaptionAnd
ImageItem testObj = new ImageItem().setCaption("caption").setSource("source"); 
 
assertEquals("captionsource", testObj.getImageLegend("")); 
} 
public void testGetImageLegendWithNullSeparatorAndCaptionAndSourceValueReturnsCaptionAndS
ImageItem testObj = new ImageItem().setCaption("caption").setSource("source"); 
 
assertEquals("captionsource", testObj.getImageLegend(null)); 
}
18

Does ImageItem#getImageLegend(String)
method responds as expected?
@Test
public void testGetImageLegendWithSeparatorAndCaptionOnlyReturnsCaptionValue() throws Exc
ImageItem testObj = new ImageItem().setCaption("caption");
assertEquals("caption", testObj.getImageLegend("SEP"));
}
@Test
public void testGetImageLegendWithSeparatorAndSourceValueOnlyReturnSourceValue() throws E
ImageItem testObj = new ImageItem().setSource("source");
assertEquals("source", testObj.getImageLegend("SEP"));
}
@Test
public void testGetImageLegendWithSeparatorAndCaptionAndSourceValueReturnsCaptionSeparate
ImageItem testObj = new ImageItem().setCaption("caption").setSource("source");
assertEquals("captionSEPsource", testObj.getImageLegend("SEP"));
}
19

How to write contract tests?
• Test code that is mocked out in collaboration tests
• Mocked interface method <—> contract test
• Verify the mock you did is valid
• Test parameters valid on interface
• Test responses (incl. exceptions) valid on interface
• Identical for different implementations
20

How to write collaboration tests?
• Test all possible responses (incl. exceptions)
• Mocked away implementation, stub in responses
• Check for result / side effect
• Test all possible parameter values
• Check for result / verify program behavior
21

Object-oriented Design,
simpliﬁed
22

If you ﬁnd a defect…
• You do have
• a missing collaboration test
• a missing contract test
• two collaboration or contract tests that don’t
agree with each other
23

How do you know its good?
• Run Fast —> Provide frequent feedback
• Small Test Setup —> Quick to implement
• Easy to maintain —> Little data dependencies
• Cover possible calls/responses —> No need to
cover all paths
• Give design feedback —> Only well designed
systems allow it
24

• Blog: “Integrated Tests Are A Scam”, J.B.
Rainsberger — http://blog.thecodewhisperer.com/
2010/10/16/integrated-tests-are-a-scam/
• Talk: “Integrated Tests Are A Scam”, J.B.
Rainsberger — https://vimeo.com/80533536
• Book: “Growing Object-Oriented Software, Guided
by Tests”, S. Freeman, N. Pryce
References
25

Thank You.
jan.wloka@quatico.com
@crashtester

Unit Testing at Scale

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