From e56cf8d9846e51ae88fa72c8b0992d81da6fd7d5 Mon Sep 17 00:00:00 2001
From: Serge Aleynikov <saleyn@gmail.com>
Date: Sat, 14 Feb 2015 17:19:17 -0500
Subject: Add ?assertReceive(Guard, Timeout) macro to eunit

A convenience macro used for testing message passing logic by allowing
to fail if a message matching a `Guard` is not received in the mailbox
of the current process.
---
 lib/eunit/doc/overview.edoc | 15 +++++++++++++++
 lib/eunit/include/eunit.hrl | 20 ++++++++++++++++++++
 2 files changed, 35 insertions(+)

diff --git a/lib/eunit/doc/overview.edoc b/lib/eunit/doc/overview.edoc
index df716cdeea..eb60f673ef 100644
--- a/lib/eunit/doc/overview.edoc
+++ b/lib/eunit/doc/overview.edoc
@@ -572,6 +572,21 @@ Examples:
 <dt>`assertNotMatch(GuardedPattern, Expr)'</dt>
 <dd>The inverse case of assertMatch, for convenience.
 </dd>
+<dt>`assertReceive(GuardedPattern, Timeout)'</dt>
+<dd>Waits for up to the `Timeout' milliseconds for a message to arrive
+in the mailbox of the current process that matches against the
+`GuardedPattern' if testing is enabled.
+If no message matching the `GuardedPattern' is received in the specified
+`Timeout' interval, the assertion fails and an informative exception will
+be generated; see the `assert' macro for further details. `GuardedPattern'
+can be anything that you can write on the left hand side of the `->'
+symbol in a case-clause, except that it cannot contain comma-separated
+guard tests.
+
+Examples:
+```?assertReceive(done, 1000)'''
+```?assertReceive(Bin when byte_size(Bin) > 10, 1000)'''
+</dd>
 <dt>`assertEqual(Expect, Expr)'</dt>
 <dd>Evaluates the expressions `Expect' and `Expr' and compares the
 results for equality, if testing is enabled. If the values are not
diff --git a/lib/eunit/include/eunit.hrl b/lib/eunit/include/eunit.hrl
index 53d291430d..8a829396ec 100644
--- a/lib/eunit/include/eunit.hrl
+++ b/lib/eunit/include/eunit.hrl
@@ -163,6 +163,26 @@
 
 -define(_assertNot(BoolExpr), ?_assert(not (BoolExpr))).
 
+%% This is mostly a convenience which gives more detailed reports.
+%% Note: Guard is a guarded pattern, and can not be used for value.
+-ifdef(NOASSERT).
+-define(assertReceive(Guard, Timeout), ok).
+-else.
+-define(assertReceive(Guard, Timeout),
+	begin
+	((fun () ->
+	    receive (Guard) -> ok
+	    after Timeout -> erlang:error({assertReceive_timedout,
+					   [{module, ?MODULE},
+					    {line, ?LINE},
+					    {pattern, (??Guard)},
+					    {timeout, __V}]})
+	    end
+	  end)())
+	end).
+-endif.
+-define(_assertReceive(Guard, Timeout), ?_test(?assertReceive(Guard, Timeout))).
+
 %% This is mostly a convenience which gives more detailed reports.
 %% Note: Guard is a guarded pattern, and can not be used for value.
 -ifdef(NOASSERT).
-- 
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