Add a failing test case and dedicated fixtures

Author: glesica

commander_unix.yaml

@@ -23,10 +23,11 @@ tests:
     command: ./commander test ./integration/unix/failing_suite.yaml
     stdout:
       contains:
+        - ✗ [local] 'file matcher should fail when file and output are different', on property 'Stdout'
         - ✗ [local] 'it will fail', on property 'ExitCode'
         - ✗ [local] 'test timeout' could not be executed with error message
         - Command timed out after 10ms
-        - "Count: 2, Failed: 2"
+        - "Count: 3, Failed: 3"
     exit-code: 1
 
   it should validate a big output:

integration/unix/_fixtures/file_output_0.txt

@@ -0,0 +1,2 @@
+first line
+second line

integration/unix/_fixtures/file_output_1.txt

@@ -0,0 +1,3 @@
+first line
+second line
+third line

integration/unix/failing_suite.yaml

@@ -7,4 +7,9 @@ tests:
     command: sleep 1
     config:
       timeout: 10ms
-    exit-code: 0
+    exit-code: 0
+
+  file matcher should fail when file and output are different:
+    command: cat ./integration/unix/_fixtures/file_output_1.txt
+    stdout:
+      file: ./integration/unix/_fixtures/file_output_0.txt