Add error message when the number of lists of errors is unexpected

src/Review/Test.elm

@@ -422,14 +422,18 @@ expectErrorsForFiles expectedErrorsList reviewResult =
             Expect.fail ErrorMessage.parsingFailure
 
         SuccessfulRun runResults ->
-            -- TODO Add expectation that we have as many elements in expectedErrorsList as runResults
-            List.map2
-                (\{ inspector, errors } expectedErrors () ->
-                    checkAllErrorsMatch inspector expectedErrors errors
-                )
-                runResults
-                expectedErrorsList
-                |> (\expectations -> Expect.all expectations ())
+            if List.length runResults /= List.length expectedErrorsList then
+                Expect.fail <| ErrorMessage.errorListLengthMismatch (List.length runResults) (List.length expectedErrorsList)
+
+            else
+                -- TODO Add expectation that we have as many elements in expectedErrorsList as runResults
+                List.map2
+                    (\{ inspector, errors } expectedErrors () ->
+                        checkAllErrorsMatch inspector expectedErrors errors
+                    )
+                    runResults
+                    expectedErrorsList
+                    |> (\expectations -> Expect.all expectations ())
 
 
 {-| Create an expectation for an error.

src/Review/Test/ErrorMessage.elm

@@ -1,7 +1,7 @@
 module Review.Test.ErrorMessage exposing
     ( ExpectedErrorData
     , parsingFailure, messageMismatch, emptyDetails, unexpectedDetails, wrongLocation, didNotExpectErrors
-    , underMismatch, expectedMoreErrors, tooManyErrors, locationIsAmbiguousInSourceCode
+    , underMismatch, expectedMoreErrors, tooManyErrors, locationIsAmbiguousInSourceCode, errorListLengthMismatch
     , missingFixes, unexpectedFixes, fixedCodeMismatch, unchangedSourceAfterFix, invalidSourceAfterFix, hasCollisionsInFixRanges
     , impossibleState
     )
@@ -13,7 +13,7 @@ module Review.Test.ErrorMessage exposing
 
 @docs ExpectedErrorData
 @docs parsingFailure, messageMismatch, emptyDetails, unexpectedDetails, wrongLocation, didNotExpectErrors
-@docs underMismatch, expectedMoreErrors, tooManyErrors, locationIsAmbiguousInSourceCode
+@docs underMismatch, expectedMoreErrors, tooManyErrors, locationIsAmbiguousInSourceCode, errorListLengthMismatch
 @docs missingFixes, unexpectedFixes, fixedCodeMismatch, unchangedSourceAfterFix, invalidSourceAfterFix, hasCollisionsInFixRanges
 @docs impossibleState
 
@@ -215,6 +215,29 @@ Tip: I found them at:
 """ ++ listOccurrencesAsLocations sourceCode under occurrencesInSourceCode
 
 
+errorListLengthMismatch : Int -> Int -> String
+errorListLengthMismatch expectedListLength actualListLength =
+    """MISMATCH BETWEEN NUMBER OF MODULES AND NUMBER OF LISTS OF ERRORS
+
+You passed a list of """ ++ String.fromInt expectedListLength ++ """ modules to this test, but a list of """ ++ String.fromInt actualListLength ++ """ lists
+of errors.
+
+I expect each item in the list of expected errors to correspond to the
+module at the same position in the module list. Since the two lists have
+different sizes, I'm not sure how to associate the last modules or errors.
+
+If you expect no errors to be reported for a module, use an empty list:
+
+  test "..." <|
+    \\() ->
+      [ sourceCode1, sourceCode2 ]
+      |> Review.Test.runMulti rule
+      |> Review.Test.expectErrorsForFiles
+          [ [] -- Expect no errors reported in `sourceCode1`
+          , [ Review.Test.error theErrorForSourceCode2 ]
+          ]"""
+
+
 impossibleState : String
 impossibleState =
     """ELM-REVIEW IMPOSSIBLE STATE

tests/ErrorMessageTest.elm

@@ -21,6 +21,7 @@ all =
         , expectedMoreErrorsTest
         , tooManyErrorsTest
         , locationIsAmbiguousInSourceCodeTest
+        , errorListLengthMismatchTest
         , missingFixesTest
         , unexpectedFixesTest
         , fixedCodeMismatchTest
@@ -587,6 +588,34 @@ Tip: I found them at:
         ]
 
 
+errorListLengthMismatchTest : Test
+errorListLengthMismatchTest =
+    test "errorListLengthMismatch" <|
+        \() ->
+            ErrorMessage.errorListLengthMismatch 1417 1418
+                |> expectMessageEqual """
+MISMATCH BETWEEN NUMBER OF MODULES AND NUMBER OF LISTS OF ERRORS
+
+You passed a list of 1417 modules to this test, but a list of 1418 lists
+of errors.
+
+I expect each item in the list of expected errors to correspond to the
+module at the same position in the module list. Since the two lists have
+different sizes, I'm not sure how to associate the last modules or errors.
+
+If you expect no errors to be reported for a module, use an empty list:
+
+  test "..." <|
+    \\() ->
+      [ sourceCode1, sourceCode2 ]
+      |> Review.Test.runMulti rule
+      |> Review.Test.expectErrorsForFiles
+          [ [] -- Expect no errors reported in `sourceCode1`
+          , [ Review.Test.error theErrorForSourceCode2 ]
+          ]
+"""
+
+
 missingFixesTest : Test
 missingFixesTest =
     test "missingFixes" <|