[Test] Luassert make sure to revert function if it is already mocked.

This commit overwrites luassert stub function to make sure that before
try to mock any function verifies that is not mocked, and if it is,
revert to the original one. This prevents scenarios where multiple stubs
are in one test and are leaked to other test and that scenario is hard
to debug/notice.

Signed-off-by: Eloy Coto <[email protected]>

spec/luassert_helper.lua

@@ -1,8 +1,33 @@
 local busted = require('busted')
 local assert = require('luassert.assert')
+local spy = require('luassert.spy')
+local stub = require('luassert.stub')
 local util = require ('luassert.util')
 local say = require('say')
 
+-- The stub.new and spy.on functions are patched here to make sure that the
+-- target function is not already a mocked function.
+-- The main reason to do that is to avoid some test that a function is mocked
+-- on  the before_each and after in the test also is mocked again, all mocks
+-- are reverted(state.revert in this module), but if the mock is double, it is
+-- only reverted once, so the first mock function will be leaked to other test.
+local original_stub_new = stub.new
+local original_spy_on = spy.on
+
+function stub.new(object, key, ...)
+  if object and spy.is_spy(object[key]) then
+    error("Stub for key='".. key .."' is already a mocked function, revert the parent function")
+  end
+  return original_stub_new(object, key, ...)
+end
+
+function spy.on(object, key)
+  if object and spy.is_spy(object[key]) then
+    error("Spy for key='".. key .."' is already a mocked function, revert the parent function")
+  end
+  return original_spy_on(object, key)
+end
+
 do -- set up reverting stubs
   local state = require("luassert.state")
 

spec/policy/3scale_batcher/3scale_batcher_spec.lua

@@ -131,6 +131,7 @@ describe('3scale batcher policy', function()
       describe('and backend is available', function()
         before_each(function()
           local backend_client = require('apicast.backend_client')
+          backend_client.authorize:revert()
           stub(backend_client, 'authorize').returns({ status = 200 })
         end)
 
@@ -144,12 +145,14 @@ describe('3scale batcher policy', function()
       describe('and backend is not available', function()
         before_each(function()
           local backend_client = require('apicast.backend_client')
+          backend_client.authorize:revert()
           stub(backend_client, 'authorize').returns({ status = 500 })
         end)
 
         describe('and the authorization is in the downtime cache', function()
           describe('and it is OK', function()
             before_each(function()
+              batcher_policy.backend_downtime_cache.get:revert()
               stub(batcher_policy.backend_downtime_cache, 'get').returns(200)
             end)
 
@@ -163,6 +166,7 @@ describe('3scale batcher policy', function()
 
           describe('and it is denied', function()
             before_each(function()
+              batcher_policy.backend_downtime_cache.get:revert()
               stub(batcher_policy.backend_downtime_cache, 'get').returns(409)
             end)
 
@@ -182,6 +186,7 @@ describe('3scale batcher policy', function()
 
         describe('and the authorization is not in the downtime cache', function()
           before_each(function()
+            batcher_policy.backend_downtime_cache.get:revert()
             stub(batcher_policy.backend_downtime_cache, 'get').returns(nil)
           end)