https://github.com/rickmoynihan/redef-methods
Stub clojure multi-method bodies
https://github.com/rickmoynihan/redef-methods
clojure integrant multi-methods stub stubbing testing
Last synced: 8 months ago
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Stub clojure multi-method bodies
- Host: GitHub
- URL: https://github.com/rickmoynihan/redef-methods
- Owner: RickMoynihan
- License: epl-2.0
- Created: 2019-02-04T12:30:09.000Z (over 6 years ago)
- Default Branch: master
- Last Pushed: 2020-06-03T07:34:49.000Z (over 5 years ago)
- Last Synced: 2025-01-29T11:37:16.237Z (8 months ago)
- Topics: clojure, integrant, multi-methods, stub, stubbing, testing
- Language: Clojure
- Homepage:
- Size: 11.7 KB
- Stars: 13
- Watchers: 4
- Forks: 1
- Open Issues: 0
-
Metadata Files:
- Readme: README.md
- License: LICENSE
Awesome Lists containing this project
README
[](https://clojars.org/tube-alloys/redef-methods)
# redef-methods
A tiny Clojure library consisting of a single macro
`with-redef-methods` that allows you to stub defmethod multi-method
bodies. Like Clojure's `with-redefs` but for `defmethods`, not vars.
## When might I use this?
The main use case is for tests, where you want to stub out a specific
defmethod for a particular dispatch value.
In particular it was written to aid testing
[integrant](https://github.com/weavejester/integrant) allowing you to
selectively stub out small parts of a larger integrant system.
The macro though is fully generic and can be used in any clojure
(1.9.0+) code base.
You could for example also use it to introduce new thread local method
dispatches. Not that I would recomend such a thing!
**WARNING**: You may run into some problems using this with `ig/load-namespaces`
and tools.namespace.
## Example
There exists a multi-method with one or more method bodies:
```clojure
(defmulti wibble (fn [key arg] key)) ;; dispatch on first argument
(defmethod wibble :foo [_ arg]
:foo-body)
(defmethod wibble :bar [_ arg]
:bar-body)
(wibble :foo 1) ;; => :foo-body
(wibble :bar 1) ;; => :bar-body
```
... and you want to stub them thread locally:
```clojure
(require '[tube-alloys.redef-methods :refer [with-redef-methods]])
(with-redef-methods [wibble {:foo (fn [key arg]
:foo-override)}]
;; Within this thread local dynamic scope (wibble :foo xxx) will trigger our
;; override function and return `:foo-override` instead of the original `defmethod`
;; body.
(wibble :foo 1) ;; => :foo-override
)
;; Outside of the binding scope we get our original implementation:
(wibble :foo 1) ;; => :foo-body
```
## With special thanks to...
[Weavejester](https://github.com/weavejester) for coming up with the
idea [whilst discussing](https://clojurians-log.clojureverse.org/duct/2019-02-01/1549034715.119700)
approaches to testing integrant systems.
## License
Copyright © 2019 Rick Moynihan
This program and the accompanying materials are made available under the
terms of the Eclipse Public License 2.0 which is available at
http://www.eclipse.org/legal/epl-2.0.