behat: add page (#3051)

pages/common/behat.md

@@ -0,0 +1,28 @@
+# behat
+
+> A PHP framework for Behaviour-Driven Development.
+> More information: <https://behat.org>.
+
+- Initialise a new Behat project:
+
+`behat --init`
+
+- Run all tests:
+
+`behat`
+
+- Run all tests from the specified suite:
+
+`behat --suite={{suite_name}}`
+
+- Run tests with a specific output formatter:
+
+`behat --format {{pretty|progress}}`
+
+- Run tests and output results to a file:
+
+`behat --out {{path/to/file}}`
+
+- Display a list of definitions in your test suites:
+
+`behat --definitions`