-For each TestCase `test_bar` of a TestSuite `test_mod.nit`, if the corresponding file `test_mod.sav/test_bar.res` exists, then the output of the test is compared with the file.
+For each TestCase `test_bar` of a TestSuite `test_mod.nit`, a corresponding file with the expected output is looked for:
+
+* "test_mod.sav/test_bar.res". I.e. test-cases grouped by test-suites.
+
+ This is the default and is useful if there is a lot of test-suites and test-cases in a directory
+
+* "sav/test_bar.res". I.e. all test-cases grouped in a common sub-directory.
+
+ Useful if there is a lot of test-suites OR test-cases in a directory.
+
+* "test_bar.res" raw in the directory.
+
+ Useful is there is a few test-suites and test-cases in a directory.
+
+All 3 are exclusive. If more than one exists, the test-case is failed.
+
+If a corresponding file then the output of the test-case is compared with the file.