peoj
Hi all,
I have a simple GenServer that performs some initialisation on start. That initialisation process involves making some calls to an HTTP API. I have delegated the HTTP communications to a lower level module, which I then mock using Mox. All well and good.
The GenServer is in my supervision tree in a vanilla sort of way so it gets started every time I run mix test. That would be fine except the GenServer starts making calls to my mock before I’ve had a chance to specify what the response should be, and mox raises a Mox.UnexpectedCallError.
So my question is; what’s the most idiomatic way of testing this? Options I’ve considered:
- Preventing applications from being manually started by using
mix test --no-startand then manually starting the pieces I need. This is fine but the auto-start behaviour is working nicely elsewhere so would add more work. - Selectively changing which processes are started depending on environment. Again this works fine.
Something tells me there is a better way. Thanks for any help!
Where Next?
Trending in Questions
Other Trending Topics
Latest on Elixir Forum
Sponsor Spotlight
We build reliable cloud platforms for business-critical systems.
Categories:
Sub Categories:
Forums
Popular Tags
- #ecto
- #liveview
- #troubleshooting
- #learning-elixir
- #library
- #deployment
- #erlang
- #testing
- #genserver
- #mix
- #absinthe
- #remote-other
- #otp
- #plug
- #how-to-question
- #macros
- #postgres
- #elixirconf
- #channels
- #exunit
- #discussion
- #code-sync
- #podcasts
- #javascript
- #onsite
- #dialyzer
- #docker
- #authentication
- #umbrella
- #full-time-contract
- #podcasts-by-brainlid
- #ai
- #ecto-query
- #elixirconf-us
- #blog-post
- #elixir-ls
- #phoenix_html
- #iex
- #graphql
- #genstage
- #websockets
- #supervisor
- #advent-of-code
- #distillery
- #processes
- #elixirconf-eu
- #api
- #forms
- #metaprogramming
- #hex
Our Sponsors
Build Elixir applications with speed and confidence.
Supporting innovation across the BEAM ecosystem.
We build reliable cloud platforms for business-critical systems.
Catch errors, track performance, monitor hosts and more.
Elixir, Erlang & BEAM conferences from Code Sync - join us in 2026!
Practical resources that improve the lives of professional developers.
Producing high quality Elixir screencasts since 2017.
The deployment platform built for Elixir: PaaS ease, VPS control.
The team behind Membrane, Popcorn, LiveDebugger. Available for hire.
Courses that'll move you from confusion to "Aha, now I get it!"
Showing Posts 1 to 4- Show Best Posts
- Show All (oldest first)
- Show All (newest first)
lud
I would have a default mock in the test.exs config and let this genserver make useless calls. And to actually test the genserver I would call its functions in my test directly, not relying on the actual process that is started in the supervision tree.
peoj
That’s pretty much as far as I’ve got but since that default mock hasn’t been configured with any expectations yet I get the
Mox.UnexpectedCallErrorsituation.How do you specify your default mock?
lud
I don’t know as I have never used a mocking library in elixir yet. If you genserver receives a module then you can implement a NoopHttpClient module maybe.
peoj
As @lud suggested I’ve ended up creating a “default mock” in the form of a stub.
I followed the instructions laid out here: Understanding Elixir mocking with Mox