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Ensuring Elixir Application Performance with Testing and ExUnit

Further Usage of List Comprehension for Test Coverage

Explore how to use list comprehensions to expand test coverage in Elixir efficiently. Understand the importance of custom failure messages for easier debugging and how to cover both positive and negative cases thoroughly using ExUnit.

We'll cover the following...

Writing custom test failure messages

While list comprehensions allow us to cover more test cases with less test code, they risk obfuscating our errors. If our test fails but we can’t tell which values it was asserting against, we’ll lose time debugging the failure. How would we know which ID we were testing when we had the wrong value of rain in the test we just wrote? Let’s update that assertion to use a custom failure message:

C++
    for {condition, ids} <- [@thunderstorm_ids, @drizzle_ids, @rain_ids] do
      test "success: recognizes #{condition} as a rainy condition" do
        # test body
        assert weather_struct.rain? == true,
              "Expected weather id (#{id}) to be a rain condition" 
      end
    end

Adding a custom error message with string interpolation (line 6) gives us everything we need to know if ...