Lazytest: A standalone test framework for Clojure

An alternative to clojure.test, aiming to be feature-rich and easily extensible.

Getting Started

Add it to your deps.edn or project.clj:

{:aliases
 {:test {:extra-deps {io.github.noahtheduke/lazytest {:mvn/version "0.4.2"}}
         :extra-paths ["test"]
         :main-opts ["-m" "lazytest.main"]}}}

In a test file:

(ns example.readme-test
  (:require [lazytest.core :refer [defdescribe describe expect it]]))

(defdescribe seq-fns-test
  (describe keep
    (it "should reject nils"
      (expect (= '(1 2 3) (keep identity [nil 1 2 3]))))
    (it "should return a sequence"
      (expect (seq? (seq (keep identity [nil])))))))

From the command line:

$ clojure -M:test

  lazytest.readme-test
    seq-fns-test
      #'clojure.core/keep
        √ should reject nils
        × should return a sequence FAIL

lazytest.readme-test
  seq-fns-test
    #'clojure.core/keep
      should return a sequence:

Expectation failed
Expected: (seq? (seq (keep identity [nil])))
Actual: nil
Evaluated arguments:
 * ()

in lazytest/readme_test.clj:11

Ran 2 test cases in 0.00272 seconds.
1 failure.

Why a new test framework?

clojure.test has existed since 1.1 and while it's both ubiquitous and useful, it has a number of problems:

• is tightly couples running test code and reporting on it.
• are is strictly worse than doseq or mapv.
• clojure.test/report is ^:dynamic, but that leads to being unable to combine multiple reporters at once, or libraries such as Leiningen monkey-patching it.
• Tests can't be grouped or bundled in any meaningful way (no, defining test-ns-hook does not count).
• testing calls aren't real contexts, they're just strings.
• Fixtures serve a real purpose but because they're set on the namespace, their definition is side-effecting and using them is complicated and hard to reuse.

There exists very good libraries like Expectations v2, kaocha, eftest, Nubank's matcher-combinators, Cognitect's test-runner that improve on clojure.test, but they're all still built on a fairly shaky foundation. I think it's worthwhile to explore other ways of being, other ways of doing stuff. Is a library like lazytest good? is a testing framework like this good when used in clojure? I don't know, but I'm willing to try and find out.

Other alternatives such as Midje, classic Expectations, and speclj attempted to correct some of those issues and they made good progress. However, some (such as Midje) relied on non-list style (test => expected) and most don't worked well with modern repl-driven development practices (as seen by the popularity of the aforementioned clojure.test-compatible Expectations v2).

I like the ideas put forth in Alessandra's post above about Lazytest and hope to experiment with achieving them 14 years later, while borrowing heavily from the work in both the Clojure community and test runners frameworks in other languages.

Usage

With the above :test alias, call clojure -M:test [options] to run your test suite once, or clojure -M:test [options] --watch to use "Watch mode" (see below) to run repeatedly as files change.

Any of the below [options] can also be provided:

• -d, --dir DIR: Directory containing tests. (Defaults to test.)
• -n, --namespace SYMBOL: Run only the specified test namespaces. Can be given multiple times.
• -v, --var SYMBOL: Run only the specified fully-qualified symbol.
• -i, --include KEYWORD: Run only test sequences or vars with this metadata keyword.
• -e, --exclude KEYWORD: Exclude test sequences or vars with this metadata keyword.
• --output SYMBOL: Output format. Can be given multiple times. (Defaults to nested.)
• --watch: As noted above, runs under "Watch mode", which reloads and reruns your test suite as project or test code changes.
• --delay NUM: How many milliseconds to wait before checking for changes to reload. Only used in "Watch mode". (Defaults to 500.)
• --help: Print help information.
• --version: Print version information.

Note: If both --namespace and --var are provided, then Lazytest will run all tests within the namespaces AND the specified vars. They are inclusive, not exclusive.

Note: --exclude overrides --include, if both are provided.

Watch mode

Watch mode uses clj-reload to reload all local changes on the classpath, plus any files containing namespaces that depend on the changed files. Watch mode defaults to lazytest.reporters/dots to make the output easier to read. By default, it checks for changes once every 500 milliseconds (1/2 a second), but this can be changed with --delay. Watch mode supports all of the other options as well, so you can select a different output style, specific directories, test namespaces, or test varsto check, etc.

Type CTRL-C to stop.

Writing tests with 'lazytest'

The primary api is found in lazytest.core namespace. It mimics the behavior-driven testing style popularized by libraries such as RSpec and Mocha.

Define tests with defdescribe, group test suites and test cases together into a suite with describe, and define test cases with it. describe can be nested. defdescribe's docstring is optional, describe and it's docstrings are not.

(defdescribe +-test "with integers"
  (it "computes the sum of 1 and 2"
    (expect (= 3 (+ 1 2))))
  (it "computes the sum of 3 and 4"
    (assert (= 7 (+ 3 4)))))

The expect macro is like assert but carries more information about the failure, such as the given form, the returned value, and the location of the call. It throws an exception if the expression does not evaluate to logical true.

If an it runs to completion without throwing an exception, the test case is considered to have passed.

Var Metadata

In addition to finding the tests defined with defdescribe, Lazytest also checks all vars for :test metadata. If the :test metadata is a function, a test case, or a test suite, it's treated as a top-level defdescribe for the associated var and executed just like other tests. :test functions are given the doc string "`:test` metadata".

How to write them:

(ns example.metadata-test ...)

(defn fn-example {:test #(expect ...)})
(defn test-case-example {:test (it "test case example docstring" ...)})
(defn suite-example {:test (suite ...)})
(defn describe-example {:test (describe "top level docstring" ...)})

How they're printed:

  example.metadata-test
    #'example.metadata-test/fn-example
      √ `:test` metadata
    #'example.metadata-test/test-case-example
      √ test case example docstring
    #'example.metadata-test/suite-example
      √ first test case
      √ second test case
    #'example.metadata-test/describe-example
      top level docstring
        √ third test case
        √ fourth test case

These can get unweildy if multiple test cases are included before a given implementation, so I recommend either moving them to a dedicated test file or moving the attr-map to the end of the function definition:

(defn describe-example
  ([a b]
   (+ a b))
  {:test (describe "Should be simple addition"
           (it "handles ints"
             (expect (= 2 (describe-example 1 1))))
           (it "handles floats"
             (expect (= 2.0 (describe-example 1.0 1.0)))))})

Focusing on Individual Tests and Suites

All of the test suite and test case macros (defdescribe, describe, it, expect-it) take a metadata map after the docstring. Adding :focus true to this map will cause only that test/suite to be run. Removing it will return to the normal behavior (run all tests).

(defdescribe my-test
  "fancy test"
  {:focus true}
  ...)

Additionally, you can use the cli option -n/--namespace to specify one or more namespaces to focus wholly, or you can use the cli option -v/--var to specify one or more fully-qualified vars to focus. This allows for testing from the command line without modifying source files.

To partition your test suite based on metadata, you can use -i/--include to only run tests with the given metadata, or -e/--exclude to skip tests with the given metadata.

Output

Lazytest comes with a number of reporters built-in. These print various information about the test run, both as it happens and surrounding execution. They are specified at the cli with --output and can be simple symbols or fully-qualified symbols. If a custom reporter is provided, it must be fully-qualified. (Otherwise, Lazytest will try to resolve it to the lazytest.reporters namespace and throw an exception.)

lazytest.reporters/nested

The default Lazytest reporter. Inspired heavily by Mocha's Spec reporter, it prints each suite and test case indented as they are written in the test files.

  lazytest.core-test
    it-test
      √ will early exit
      √ arbitrary code
    with-redefs-test
      redefs inside 'it' blocks
        × should be rebound FAIL
      redefs outside 'it' blocks
        √ should not be rebound

lazytest.core-test
  with-redefs-test
    redefs inside 'it' blocks
      should be rebound:

this should be true
Expected: (= 7 (plus 2 3))
Actual: false
Evaluated arguments:
 * 7
 * 6
Only in first argument:
7
Only in second argument:
6

in lazytest/core_test.clj:29

Ran 90 test cases in 0.06548 seconds.
1 failure.

lazytest.reporters/dots

A minimalist reporter. Prints passing test cases as green . and failures as red F during the test run. Test suites are grouped with parentheses ((/)). It also prints the failure results and summary as in lazytest.reporters/nested, which has been elided below for brevity.

(...)(..F................)(.....)(..)(..)(....)(........)(........................................)(.......)

lazytest.reporters/clojure-test

Mimics clojure.test's default reporter, treating suite and test-case docstrings as testing strings.

Testing lazytest.core-test

FAIL in (with-redefs-test) (lazytest/core_test.clj:29)
with-redefs-test redefs inside 'it' blocks should be rebound
this should be true
expected: (= 7 (plus 2 3))
  actual: false

Ran 25 tests containing 90 test cases.
1 failure, 0 errors.

lazytest.reporters/quiet

Prints nothing. Useful if all you want is the return code.

lazytest.reporters/debug

Prints loudly about every step of the run. Incredibly noise, not recommended for anything other than debugging Lazytest internals.

Editor Integration

The entry-points are at lazytest.repl: run-all-tests, run-tests, and run-test-var. The first runs all loaded test namespaces, the second runs the provided namespaces (either a single namespace or a collection of namespaces), and the third runs a single test var. If your editor can define custom repl functions, then it's fairly easy to set these as your test runner.

Example configuration

Neovim with Conjure:

-- in your init.lua
local runners = require("conjure.client.clojure.nrepl.action")
runners["test-runners"].lazytest = {
  ["namespace"] = "lazytest.repl",
  ["all-fn"] = "run-all-tests",
  ["ns-fn"] = "run-tests",
  ["single-fn"] = "run-test-var",
  ["default-call-suffix"] = "",
  ["name-prefix"] = "#'",
  ["name-suffix"] = ""
}
vim.g["conjure#client#clojure#nrepl#test#runner"] = "lazytest"

VSCode with Calva:

"calva.customREPLCommandSnippets": [
    {
        "name": "Lazytest: Test All Tests",
        "snippet": "(lazytest.repl/run-all-tests)"
    },
    {
        "name": "Lazytest: Test Current Namespace",
        "snippet": "(lazytest.repl/run-tests $editor-ns)"
    },
    {
        "name": "Lazytest: Test Current Var",
        "snippet": "(lazytest.repl/run-test-var #'$top-level-defined-symbol)"
    }
],

IntelliJ with Cursive:

Name: Lazytest - Test All Tests
Execute Command: (lazytest.repl/run-all-tests)
Execution Namespace: Execute in current file namespace
Results: Print results to REPL output

Name: Lazytest - Test Current Namespace
Execute Command: (lazytest.repl/run-tests ~file-namespace)
Execution Namespace: Execute in current file namespace
Results: Print results to REPL output

Name: Lazytest - Test Current Var
Execute Command: (lazytest.repl/run-test-var #'~current-var)
Execution Namespace: Execute in current file namespace
Results: Print results to REPL output

Lazytest Internals

The smallest unit of testing is a test case, which is a function (see lazytest.test-case/test-case). When the function is called, it may throw an exception to indicate failure. If it does not throw an exception, it is assumed to have passed. The return value of a test case is always ignored. Running a test case may have side effects.

NOTE: The macros lazytest.describe/it and lazytest.describe/expect-it create test cases.

Tests cases are organized into suites. A test suite is a function (see lazytest.suite/suite) that returns a test sequence. A test sequence (see lazytest.suite/test-seq) is a sequence, possibly lazy, of test cases and/or test suites. Suites, therefore, may be nested inside other suites, but nothing may be nested inside a test case.

NOTE: The macros lazytest.describe/defdescribe and lazytest.describe/describe create test suites.

A test suite function SHOULD NOT have side effects; it is only used to generate test cases and/or other test suites.

A test runnner is responsible for expanding suites (see lazytest.suite/expand-suite) and running test cases (see lazytest.test-case/try-test-case). It may also provide feedback on the success of tests as they run.

The test runner also returns a sequence of results, which are either suite results (see lazytest.suite/suite-result) or test case results (see lazytest.test-case/test-case-result). That sequence of results is passed to a reporter, which formats results for display to the user. Multiple reporters are provided, see the namespace lazytest.reporters.

License

Originally by Alessandra Sierra.

Currently developed by Noah Bogart.

Licensed under Eclipse Public License 1.0