X-Git-Url: http://nitlanguage.org

diff --git a/share/man/nitunit.md b/share/man/nitunit.md
index 4e4ea82..e80e80e 100644
--- a/share/man/nitunit.md
+++ b/share/man/nitunit.md
@@ -169,6 +169,34 @@ class TestFoo
 end
 ~~~~
 
+## Black Box Testing
+
+Sometimes, it is easier to validate a `TestCase` by comparing its output with a text file containing the expected result.
+
+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.
+
+The `diff(1)` command is used to perform the comparison.
+The test is failed if non-zero is returned by `diff`.
+
+~~~
+module test_mod is test_suite
+class TestFoo
+	fun test_bar do
+		print "Hello!"
+	end
+end
+~~~
+
+Where `test_mod.sav/test_bar.res` contains
+
+~~~raw
+Hello!
+~~~
+
+If no corresponding `.res` file exists, then the output of the TestCase is ignored.
+
+## Configuring TestSuites
+
 `TestSuites` also provide methods to configure the test run:
 
 `before_test` and `after_test`: methods called before/after each test case.
@@ -284,6 +312,29 @@ Only display the skeleton, do not write any file.
 
 Indicate the specific Nit compiler executable to use. See `--nitc`.
 
+### `NIT_TESTING`
+
+The environment variable `NIT_TESTING` is set to `true` during the execution of program tests.
+Some libraries of programs can use it to produce specific reproducible results; or just to exit their executions.
+
+Unit-tests may unset this environment variable to retrieve the original behavior of such piece of software.
+
+### `SRAND`
+
+In order to maximize reproducibility, `SRAND` is set to 0.
+This make the pseudo-random generator no random at all.
+See `Sys::srand` for details.
+
+To retrieve the randomness, unit-tests may unset this environment variable then call `srand`.
+
+### `NIT_TESTING_ID`
+
+Parallel executions can cause some race collisions on named resources (e.g. DB table names).
+To solve this issue, `NIT_TESTING_ID` is initialized with a distinct integer identifier that can be used to give unique names to resources.
+
+Note: `rand` is not a recommended way to get a distinct identifier because its randomness is disabled by default. See `SRAND`.
+
+
 # SEE ALSO
 
 The Nit language documentation and the source code of its tools and libraries may be downloaded from <http://nitlanguage.org>