Improvements to ExUnit

* Do not run duplicate cases on ExUnit.run/1
* Allow test cases to not be registered on use
* Expose ExUnit.Formatter.format_assertion_diff/4

Author: josevalim

lib/ex_unit/lib/ex_unit.ex

@@ -201,7 +201,7 @@ defmodule ExUnit do
 
       System.at_exit(fn
         0 ->
-          time = ExUnit.Server.modules_loaded()
+          time = ExUnit.Server.modules_loaded(false)
           options = persist_defaults(configuration())
           %{failures: failures} = ExUnit.Runner.run(options, time)
 
@@ -373,7 +373,7 @@ defmodule ExUnit do
       end
     end
 
-    _ = ExUnit.Server.modules_loaded()
+    _ = ExUnit.Server.modules_loaded(additional_modules != [])
     options = persist_defaults(configuration())
     ExUnit.Runner.run(options, nil)
   end
@@ -399,7 +399,7 @@ defmodule ExUnit do
   @doc since: "1.12.0"
   @spec await_run(Task.t()) :: suite_result()
   def await_run(task) do
-    ExUnit.Server.modules_loaded()
+    ExUnit.Server.modules_loaded(false)
     Task.await(task, :infinity)
   end
 

lib/ex_unit/lib/ex_unit/assertions.ex

@@ -260,19 +260,21 @@ defmodule ExUnit.Assertions do
     quote do
       left = unquote(left)
       right = unquote(right)
+      expr = unquote(expr)
+      message = unquote(message)
 
       if ExUnit.Assertions.__equal__?(left, right) do
         ExUnit.Assertions.assert(false,
           left: left,
-          expr: unquote(expr),
-          message: unquote(message <> ", both sides are exactly equal")
+          expr: expr,
+          message: message <> ", both sides are exactly equal"
         )
       else
         ExUnit.Assertions.assert(unquote(call),
           left: left,
           right: right,
-          expr: unquote(expr),
-          message: unquote(message),
+          expr: expr,
+          message: message,
           context: unquote(context)
         )
       end

lib/ex_unit/lib/ex_unit/case.ex

@@ -284,7 +284,7 @@ defmodule ExUnit.Case do
         raise "you must set @tag, @describetag, and @moduletag after the call to \"use ExUnit.Case\""
       end
 
-      attributes = [
+      accumulate_attributes = [
         :ex_unit_tests,
         :tag,
         :describetag,
@@ -294,24 +294,23 @@ defmodule ExUnit.Case do
         :ex_unit_registered_module_attributes
       ]
 
-      Enum.each(attributes, &Module.register_attribute(module, &1, accumulate: true))
+      Enum.each(accumulate_attributes, &Module.register_attribute(module, &1, accumulate: true))
 
       persisted_attributes = [:ex_unit_async]
+
       Enum.each(persisted_attributes, &Module.register_attribute(module, &1, persist: true))
 
-      attributes = [
-        before_compile: ExUnit.Case,
-        after_compile: ExUnit.Case,
-        ex_unit_async: false
-      ]
+      if Keyword.get(opts, :register, true) do
+        Module.put_attribute(module, :after_compile, ExUnit.Case)
+      end
 
-      Enum.each(attributes, fn {k, v} -> Module.put_attribute(module, k, v) end)
+      Module.put_attribute(module, :before_compile, ExUnit.Case)
     end
 
     async? = opts[:async]
 
-    if is_boolean(async?) do
-      Module.put_attribute(module, :ex_unit_async, async?)
+    if is_boolean(async?) or not registered? do
+      Module.put_attribute(module, :ex_unit_async, async? || false)
     end
 
     registered?