Warn users if verifying an exact stubbing

Fixes #76

src/verify.coffee

@@ -1,13 +1,16 @@
 _ = require('lodash')
 store = require('./store')
 callsStore = require('./store/calls')
+stubbingsStore = require('./store/stubbings')
 stringifyArgs = require('./stringify/arguments')
 log = require('./log')
+argsMatch = require('./args-match')
 
 module.exports = (__userDoesPretendInvocationHere__, config = {}) ->
   if last = callsStore.pop()
     if callsStore.wasInvoked(last.testDouble, last.args, config)
       # Do nothing! We're verified! :-D
+      warnIfStubbed(last.testDouble, last.args)
     else
       log.fail(unsatisfiedErrorMessage(last.testDouble, last.args, config))
   else
@@ -18,6 +21,15 @@ module.exports = (__userDoesPretendInvocationHere__, config = {}) ->
           verify(myTestDouble('foo'))
       """
 
+warnIfStubbed = (testDouble, actualArgs) ->
+  _.find stubbingsStore.for(testDouble), (stubbing) ->
+    if argsMatch(stubbing.args, actualArgs, allowMatchers: false)
+      log.warn 'td.verify', """
+      test double#{stringifyName(testDouble)} was both stubbed and verified with arguments (#{stringifyArgs(actualArgs)}), which is redundant and probably unnecessary.
+      """, "https://github.com/testdouble/testdouble.js/blob/master/docs/B-frequently-asked-questions.md#why-shouldnt-i-call-both-tdwhen-and-tdverify-for-a-single-interaction-with"
+      true
+
+
 unsatisfiedErrorMessage = (testDouble, args, config) ->
   """
   Unsatisfied verification on test double#{stringifyName(testDouble)}.
@@ -26,6 +38,11 @@ unsatisfiedErrorMessage = (testDouble, args, config) ->
       - called with `(#{stringifyArgs(args)})`#{timesMessage(config)}.
   """ + invocationSummary(testDouble)
 
+stringifyName = (testDouble) ->
+  if name = store.for(testDouble).name
+    " `#{name}`"
+  else
+    ""
 invocationSummary = (testDouble) ->
   calls = callsStore.for(testDouble)
   if calls.length == 0
@@ -35,12 +52,6 @@ invocationSummary = (testDouble) ->
       desc + "\n    - called with `(#{stringifyArgs(call.args)})`."
     , "\n\n  But was actually called:"
 
-stringifyName = (testDouble) ->
-  if name = store.for(testDouble).name
-    " `#{name}`"
-  else
-    ""
-
 timesMessage = (config) ->
   return "" unless config.times?
   " #{config.times} time#{if config.times == 1 then '' else 's'}"

test/src/verify-test.coffee

@@ -155,3 +155,25 @@ describe '.verify', ->
               - called with `()`.
               - called with `()`.
           """
+
+  describe 'warning when verifying a stubbed invocation', ->
+    Given -> @ogWarn = console.warn
+    Given -> @warnings = []
+    Given -> console.warn = (msg) => @warnings.push(msg)
+    afterEach = console.warn = @ogWarn
+    Given -> @td = td.function('.foo')
+
+    context 'an exact match in calls', ->
+      Given -> td.when(@td(1)).thenReturn(5)
+      Given -> @td(1)
+      When -> td.verify(@td(1))
+      Then -> @warnings[0] == """
+        Warning: testdouble.js - td.verify - test double `.foo` was both stubbed and verified with arguments (1), which is redundant and probably unnecessary. (see: https://github.com/testdouble/testdouble.js/blob/master/docs/B-frequently-asked-questions.md#why-shouldnt-i-call-both-tdwhen-and-tdverify-for-a-single-interaction-with )
+        """
+
+    context 'matchers are used', ->
+      Given -> td.when(@td(td.matchers.isA(Number))).thenReturn(5)
+      Given -> @td(1)
+      When -> td.verify(@td(1))
+      Then -> @warnings.length == 0
+