Add documentation about the testing framework

tests/README.md

@@ -1,7 +1,56 @@
-#### Running tests
+### Running tests
 
 To run all tests, simply run `./run_all`.
 Also see section in general README [here](../README.md#testing)
 
-#### Writing tests
-[See here](https://github.com/Unode/firefox_decrypt/pull/6#issuecomment-228809588)
+### Writing tests
+
+Tests are executed using the [bash-tap](https://github.com/wbsch/bash_tap) testing framework.
+
+#### Requirements
+
+Tests must meet the following criteria:
+- A test must have a `.t` extension.
+- In order to be picked up by the `run_all` script, the test must also be executable. (`chmod +x testfile.t`)
+
+#### Test structure
+
+Test files contain the following:
+
+    #!/usr/bin/env bash
+
+    # File containing all testing functionality and helper functions
+    . bash_tap_fd.sh
+
+    # Obtain master password used in the test framework
+    PASSWD=$(get_password)
+    # Basically the firefox_decrypt.py command
+    CMD=$(get_script)
+    # Test data to use. One of the profiles under tests/test_data/ or the test_data folder itself in which case profile.ini is used.
+    TEST="$(get_test_data)"
+    # For interactive tests this consists of the commands that a user would type
+    PAYLOAD="2\n${PASSWD}"
+
+    # Each line is one test. If the line has a non-zero exit code the test fails
+    echo ${PAYLOAD} | ${CMD} --args ${TEST} ...
+    # Some tests also use diff and grep to ensure the output matches what is expected
+
+
+#### Syntax
+
+Some tests make use of some lesser known bash constructs such as `<(command)`.
+This syntax is called **process substitution** and is documented [here](http://www.tldp.org/LDP/abs/html/process-sub.html).
+
+#### Existing test profiles
+
+In order to test compatibility with different versions of Firefox there are currently 3 profiles that can be picked from:
+- `test_profile_firefox_20` - Firefox 20.0 (uses an sqlite storage backend for secrets)
+- `test_profile_firefox_46` - Firefox 46.0 (uses a json storage backend for secrets)
+- `test_profile_firefox_nopassword` - Firefox 46.0 (secrets are not protected by a master password)
+
+The password used in the protected profiles lives in `tests/test_data/master_password` and can be obtained by calling the `get_password` helper function in tests.
+
+#### Logins
+
+Each testing profile contains 3 users. Their details are found under `tests/test_data/users/`.
+These can be used to validate that `firefox_decrypt` outputs the correct answer, including encoding and handling of special characters.