Remove Iris' TestRunner (#5205)

Author: lbdreyer

docs/src/whatsnew/latest.rst

@@ -137,6 +137,9 @@ This document explains the changes made to Iris for this release
 #. `@lbdreyer`_ and `@trexfeathers`_ (reviewer) removed the ``--coding-tests``
    option from Iris' test runner. (:pull:`4765`)
 
+#. `@lbdreyer`_ removed the Iris TestRunner. Tests are now run via nox or
+   pytest. (:pull:`5205`)
+
 
 .. comment
     Whatsnew author names (@github name) in alphabetical order. Note that,

lib/iris/config.py

@@ -171,8 +171,7 @@ def get_dir_option(section, option, default=None):
 )
 
 # Override the data repository if the appropriate environment variable
-# has been set.  This is used in setup.py in the TestRunner command to
-# enable us to simulate the absence of external data.
+# has been set.
 override = os.environ.get("OVERRIDE_TEST_DATA_REPOSITORY")
 if override:
     TEST_DATA_DIR = None

lib/iris/tests/runner/__init__.py

@@ -188,13 +188,13 @@ def tests(session: nox.sessions.Session):
     session.install("--no-deps", "--editable", ".")
     session.env.update(ENV)
     run_args = [
-        "python",
-        "-m",
-        "iris.tests.runner",
-        "--default-tests",
+        "pytest",
+        "-n",
+        "auto",
+        "lib/iris/tests",
     ]
     if "-c" in session.posargs or "--coverage" in session.posargs:
-        run_args.append("--coverage")
+        run_args[-1:-1] = ["--cov=lib/iris", "--cov-report=xml"]
     session.run(*run_args)
 
 
@@ -241,10 +241,10 @@ def gallery(session: nox.sessions.Session):
     session.install("--no-deps", "--editable", ".")
     session.env.update(ENV)
     session.run(
-        "python",
-        "-m",
-        "iris.tests.runner",
-        "--gallery-tests",
+        "pytest",
+        "-n",
+        "auto",
+        "docs/gallery_tests",
     )