clojure.test for Expectations

A clojure.test-compatible version of the classic Expectations testing library.

What?

This library brings expect, more, more-of, etc from Expectations into the clojure.test world to be used instead of (or in addition to) the familiar is macro. This library has no dependencies, other than clojure.test itself, and should be compatible with all existing clojure.test-based tooling in editors and command-line tools.

You can either use deftest from clojure.test, or defexpect from this library to wrap your tests.

(ns my.cool.project-test
  (:require [clojure.test :refer [deftest is]]
            [expectations.clojure.test :refer :all]))

;; mix'n'match libraries:

(deftest mixed
  (is 2 (+ 1 1))
  (expect even? (+ 1 1)))

;; simple equality tests:

(defexpect equality
  (expect 1 (* 1 1))
  (expect "foo" (str "f" "oo")))

;; the expected outcome can be a regular expression:

(defexpect regex-1
  (expect #"foo" "It's foobar!"))

;; since that has only a single expectation, it can be written more succinctly:

(defexpect regex-2 #"foo" "It's foobar!")

;; the expected outcome can be an exception type:

(defexpect divide-by-zero ArithmeticException (/ 12 0))

;; the expected outcome can be a predicate:

(defexpect no-elements empty? (list))

;; the expected outcome can be a type:

(defexpect named String (name :foo))

;; if the actual value is a collection, the expected outcome can be an element or subset "in" that collection:

(defexpect collections
  (expect {:foo 1} (in {:foo 1 :cat 4}))
  (expect :foo (in #{:foo :bar}))
  (expect :foo (in [:bar :foo])))

Just like deftest, the defexpect macro creates a function that contains the test(s). You can run each function individually:

user=> (equality)
nil

If the test passes, nothing is printed, and nil is returned. Let's look at a failing test:

user=> (defexpect inequality (* 2 21) (+ 13 13 13))
#'user/inequality
user=> (inequality)

FAIL in (inequality) (.../README.md:67)
expected: (=? (* 2 21) (+ 13 13 13))
  actual: 39
nil

The output is produced by clojure.test's standard reporting functionality. The =? operator is an extension to clojure.test's assert-expr multimethod that allows for Expectations style of predicate-or-equality testing (based on whether the "expected" expression resolves to a function or some other value):

user=> (defexpect indivisible odd? (+ 1 1))
#'user/indivisible
user=> (indivisible)

FAIL in (indivisible) (.../README.md:83)
expected: (=? odd? (+ 1 1))
  actual: (not (odd? 2))
nil

Here we see the predicate (odd?) being applied in the "actual" result from clojure.test.

expectations.clojure.test supports the following features from Expectations so far:

• simple equality test
• simple predicate test
• class test -- see named above
• exception test -- see divide-by-zero above
• regex test -- see regex-1 and regex-2 above
• (expect expected-expr (from-each [a values] (actual-expr a)))
• (expect expected-expr (in actual-expr)) -- see collections above
• (expect (more-of destructuring e1 a1 e2 a2 ...) actual-expr)
• (expect (more-> e1 a1 e2 a2 ...) actual-expr) -- where actual-expr is threaded into each a1, a2, ... expression
• (expect (more e1 e2 ...) actual-expr)
• (expect expected-expr (side-effects [fn1 fn2 ...] actual-expr))

Read the Expectations documentation for more details of these features.

Tests defined with defexpect behave just like tests defined with deftest and all of the existing clojure.test-based tooling will work with them, including fixtures, test runners, and other libraries that patch clojure.test to improve its error reporting and other features.

Why?

Given the streamlined simplicity of Expectations, you might wonder why you would want to migrate your Expectations test suite to clojure.test-style named tests? The short answer is tooling! Whilst Expectations has well-maintained, stable plugins for Leiningen and Boot, as well as an Emacs mode, the reality is that Clojure tooling is constantly evolving and most of those tools -- such as the excellent https://cider.readthedocs.io/en/latest/, https://cursive-ide.com/, and the more recent https://atom.io/packages/proto-repl and Chlorine (both for Atom) -- are going to focus on Clojure's built-in testing library first. Support for the original form of Expectations, using unnamed tests, is non-existent in Cursive, and can be problematic in other editors.

A whole ecosystem of tooling has grown up around clojure.test and to take advantage of that with Expectations, we either need to develop compatible extensions to each and every tool or we need Expectations to be compatible with clojure.test.

One of the big obstacles for that compatibility is that, by default, Expectations generates "random" function names for test code (the function names are based on the hashcode of the text form of the expect body), which means the test name changes whenever the text of the test changes. To address that, the new expectations.clojure.test namespace introduces named expectations via the defexpect macro (mimicking clojure.test's deftest macro). Whilst this goes against the [https://clojure-expectations.github.io/odds-ends.html](Test Names philosophy) that Expectations was created with, it buys us a lot in terms of tooling support!

Differences from Expectations

Aside from the obvious difference of providing names for tests -- essential for compatibility with clojure.test-based tooling -- here are the other differences to be aware of:

• You use standard clojure.test-based tooling -- lein test, boot test, and Cognitect's test-runner -- instead of the Expectations-specific tooling.
• Because of that, tests run when you decide, not at JVM shutdown (which is the default with Expectations).
• Instead of the in-context, before-run, after-run machinery of Expectations, you can just use clojure.test's fixtures machinery (use-fixtures).
• Instead of Expectations' concept of "focused" test, you can use metadata on tests and tell your test runner to "select" tests as needed (e.g., Leiningen's "test selectors", Boot's "filters").
• freeze-time and redef-state are not (yet) implemented.
• The undocumented CustomPred protocol is not implemented -- you can use plain is and extend clojure.test's assert-expr multimethod if you need that level of control.

Test & Development

To test, run clj -A:test:runner.

TODO

Add tests(!) and more examples.

License & Copyright

Copyright © 2018-2019 Sean Corfield, all rights reserved.

Distributed under the Eclipse Public License version 1.0.