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dhemery/hamcrest-matcher-style.java

Created December 10, 2011 00:25
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DSLs to verify and wait for conditions: Which style do you prefer?
Raw
hamcrest-matcher-style.java
verifyThat(masterView, isPresent());
verifyThat(masterView, eventually(isPresent()));
// What would the "when the subject satisfies a condition" example look like? Maybe this?
when(masterView, isPresent()).touch();
Raw
noun-first-dsl.java
masterView.verify().isPresent();
masterView.verify().eventually().isPresent();
masterView.whenPresent().touch();
Raw
sentence-like-dsl.java
verifyThat(masterView).isPresent();
verifyThat(masterView).eventually().isPresent();
when(masterView).isPresent().touch();
Raw
sentence-template-dsl.java
// Assertions
assertThat(SUBJECT).is(IN_SOME_CONDITION);
assertThat(SUBJECT).has(ATTRIBUTE, IN_SOME_CONDITION);
assertThat(SUBJECT).has(ATTRIBUTE).that(MATCHES_SOME_CRITERIA);
// Polled assertions
assertThat(SUBJECT).eventually().is(IN_SOME_CONDITION);
assertThat(SUBJECT).eventually().has(ATTRIBUTE, IN_SOME_CONDITION);
assertThat(SUBJECT).eventually().has(ATTRIBUTE).that(MATCHES_SOME_CRITERIA);
// Polled conditions
waitUntil(SUBJECT).is(IN_SOME_CONDITION);
waitUntil(SUBJECT).has(ATTRIBUTE, IN_SOME_CONDITION);
waitUntil(SUBJECT).has(ATTRIBUTE).that(MATCHES_SOME_CRITERIA);
// Polled preconditions
when(SUBJECT).is(IN_SOME_CONDITION).TAKE_AN_ACTION();
when(SUBJECT).has(ATTRIBUTE, IN_SOME_CONDITION).TAKE_AN_ACTION();
when(SUBJECT).has(ATTRIBUTE).that(MATCHES_SOME_CRITERIA).TAKE_AN_ACTION();
// SUBJECT is any object that implements SelfDescribing.
//
// ATTRIBUTE is a sampler that samples the value of some aspect
// of a subject. Typical use supplies ATTRIBUTE via a factory method.
//
// IN_SOME_CONDITION and MATCHES_SOME_CRITERIA are matchers that evaluate
// either the subject or a sampled value. Typical use supplies the matcher
// via a factory method.
//
// TAKE_AN_ACTION is any method of SUBJECT.
// The two forms of has() function similarly. They differ only in
// sentence structure and diagnostics: The ".that()" form injects
// the word "that" into the diagnostic message.
@jbrains
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jbrains commented Dec 10, 2011

I prefer verifyThat(object).method() because code completion helps more.

@dhemery
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dhemery commented Dec 10, 2011

Yeah, I'm trying to write some real tests in Hamcrest style, and I feel buried under nested parentheses:
assertThat(masterView, eventually(is(not(present()))));

@npryce
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npryce commented Dec 11, 2011

I would make the action something passed in too. E.g.

when(masterView, both(isPresent(), displaysText("Ready!")), tap())

This means you don't need to repeat the wait condition in order to do multiple things to a screen element. And you can compose gestures out of gestures.

E.g.:

Gesture tap = sequence(touch(), shortDelay(), release())
Gesture doubleTap = sequence(tap, shortDelay(), tap)
when(masterView, both(isPresent(), displaysText("Ready!")), doubleTap)

I see your point about nested parentheses, although I configure my IDE to color parentheses pale grey and names black so they don't bother me very much! But you could chain methods together to act like keywords:

when(masterView).is(present(), displayingText("Ready!")).then(doubleTap);

This is now looking very like WebLicker. I thought it was very cool :-). But I found in practice that I needed the DSL at the layer above -- to express in the tests what was being tested -- and a DSL style at the "how it is being tested" level rather got in the way of that.

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