Add a very simple wrapper (in_series) around :meck.seq (#132)

tpitale · web-flow · commit 84abb395d7d3 · 2022-01-23T15:04:23.000-05:00
diff --git a/README.md b/README.md
@@ -18,6 +18,7 @@ See the full [reference documentation](https://hexdocs.pm/mock/Mock.html).
 	* [*setup_with_mocks* - Configure all tests to have the same mocks](#setup_with_mocks---Configure-all-tests-to-have-the-same-mocks)
 	* [Mocking input dependent output](#Mocking-input-dependent-output)
 	* [Mocking functions with different arities](#Mocking-functions-with-different-arities)
+	* [Mocking repeated calls to the same function with different results](#Mocking-repeated-calls-to-the-same-function)
 	* [*passthrough* - partial mocking of a module](#passthrough---partial-mocking-of-a-module)
 	* [Assert called - assert a specific function was called](#Assert-called---assert-a-specific-function-was-called)
 		* [Assert called - specific value](#Assert-called---specific-value)
@@ -204,7 +205,7 @@ defmodule MyTest do
       assert Map.get(%{}, "http://example.tech") == "<html>example.tech says hi</html>"
     end
   end
-  
+
   def conditionally_mocked(url) do
     cond do
       String.contains?(url, ".xyz") -> "<html>Hello from example.xyz</html>"
@@ -237,6 +238,35 @@ end
 
 ````
 
+## Mock repeated calls
+
+You can mock repeated calls to the same function _and_ arguments to return
+different results in a series using the `in_series` call with static values.
+This does not currently support _functions_.
+
+**Caution**: This is only useful in rare instances where the underlying business
+logic is likely to be stateful. If you can avoid it by using different function
+arguments, or refactor the function to be stateful, consider that approach first.
+
+```` elixir
+defmodule MyTest do
+  use ExUnit.Case, async: false
+
+  import Mock
+
+  test "mock repeated calls with in_series" do
+    with_mock String,
+      [slice: [in_series(["test", 1..3], ["string1", "string2", "string3"])]]
+    do
+      assert String.slice("test", 1..3) == "string1"
+      assert String.slice("test", 1..3) == "string2"
+      assert String.slice("test", 1..3) == "string3"
+    end
+  end
+end
+
+````
+
 ## *passthrough* - partial mocking of a module
 
 By default, only the functions being mocked can be accessed from within the test.
diff --git a/lib/mock.ex b/lib/mock.ex
@@ -366,4 +366,8 @@ defmodule Mock do
     :meck.expect(mock_module, fn_name, value)
     _install_mock(mock_module, tail)
   end
+
+  def in_series(signature, results) do
+    {signature, :meck.seq(results)}
+  end
 end
diff --git a/test/mock_test.exs b/test/mock_test.exs
@@ -64,6 +64,21 @@ defmodule MockTest do
     assert result == 6
   end
 
+  test "mock returns multiples results in sequence" do
+    with_mock String, [
+      reverse: [in_series([:_], [:a, :b, :c])],
+      slice: [in_series([1, 2], [:x, :y, :z])]
+    ] do
+      assert String.reverse(1) == :a
+      assert String.reverse(1) == :b
+      assert String.reverse(1) == :c
+
+      assert String.slice(1, 2) == :x
+      assert String.slice(1, 2) == :y
+      assert String.slice(1, 2) == :z
+    end
+  end
+
   test "called" do
     with_mock String,
        [reverse: fn(x) -> 2*x end,
