expand and rewrite testsbug23091

make it more obvious what we are testing and handle more cases

1 files changed, 27 insertions, 9 deletions

diff --git a/src/rabbit_tests.erl b/src/rabbit_tests.erl
index e6a43120..c07055af 100644
--- a/src/rabbit_tests.erl
+++ b/src/rabbit_tests.erl
@@ -538,6 +538,9 @@ test_content_framing() ->
     passed.
 
 test_content_transcoding() ->
+    %% there are no guarantees provided by 'clear' - it's just a hint
+    ClearDecoded = fun rabbit_binary_parser:clear_decoded_content/1,
+    ClearEncoded = fun rabbit_binary_generator:clear_encoded_content/1,
     EnsureDecoded =
         fun (C0) ->
                 C1 = rabbit_binary_parser:ensure_content_decoded(C0),
@@ -553,17 +556,32 @@ test_content_transcoding() ->
                         C1
                 end
         end,
-    EnsureEncoded1 = EnsureEncoded(rabbit_framing_amqp_0_9_1),
-    EnsureEncoded2 = EnsureEncoded(rabbit_framing_amqp_0_8),
-    ClearEncoded = fun rabbit_binary_generator:clear_encoded_content/1,
-    ClearDecoded = fun rabbit_binary_parser:clear_decoded_content/1,
-    lists:foldl(fun (F, V) -> F(F(V)) end,
-                rabbit_basic:build_content(#'P_basic'{}, <<>>),
-                [EnsureDecoded, ClearEncoded, ClearDecoded,
-                 EnsureEncoded1, ClearDecoded, ClearEncoded,
-                 EnsureEncoded2, EnsureDecoded, ClearEncoded, EnsureEncoded1]),
+    %% Beyond the assertions in Ensure*, the only testable guarantee
+    %% is that the operations should never fail.
+    %%
+    %% If we were using quickcheck we'd simply stuff all the above
+    %% into a generator for sequences of operations. In the absence of
+    %% quickcheck we pick particularly interesting sequences that:
+    %%
+    %% - execute every op twice since they are idempotent
+    %% - invoke clear_decoded, clear_encoded, decode and transcode
+    %%   with one or both of decoded and encoded content present
+    [begin
+         sequence_with_content([Op]),
+         sequence_with_content([ClearEncoded, Op]),
+         sequence_with_content([ClearDecoded, Op])
+     end || Op <- [ClearDecoded, ClearEncoded, EnsureDecoded,
+                   EnsureEncoded(rabbit_framing_amqp_0_9_1),
+                   EnsureEncoded(rabbit_framing_amqp_0_8)]],
     passed.
 
+sequence_with_content(Sequence) ->
+    lists:foldl(fun (F, V) -> F(F(V)) end,
+                rabbit_binary_generator:ensure_content_encoded(
+                  rabbit_basic:build_content(#'P_basic'{}, <<>>),
+                  rabbit_framing_amqp_0_9_1),
+                Sequence).
+
 test_topic_match(P, R) ->
     test_topic_match(P, R, true).