Today I Learned

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Updating the ExUnit test context with setup

When using ExUnit the second argument to the test macro is context.

test "1 + 1 = value", context do
  assert 1 + 1 == 2
end

This context can provide setup values so that you can share setup across tests.

Use the setup macro to update the context. The keyword list you return from the setup function will be merged into the map of the context.

setup do
  [result: 2]  # this gets merged into the context
end

setup do
  # create some database records
  :ok # this does not get merged into the context
end

Also in the setup macro you can have access to the context, allowing you to potentially change the context based on the needs of the test.

setup context do
  %{result: r} = context
    [result: r + 1]
end

test "1 + 1 = value", %{result: value} do
  assert 1 + 1 == value
end

Read more about ExUnit setup here.

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