selftest/seltest.py: Add test to check imports from other layers

This tests adds a check of selftest itself to verify if can
add test from other layers.

[YOCTO #9770]

(From OE-Core rev: 4fe4c408246b9a4a563106d097876e6caefca694)

Signed-off-by: Mariano Lopez <mariano.lopez@linux.intel.com>
Signed-off-by: Jose Perez Carranza <jose.perez.carranza@linux.intel.com>
Signed-off-by: Ross Burton <ross.burton@intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

meta-selftest/lib/oeqa/selftest/cases/external-layer.py

@@ -0,0 +1,16 @@
+#from oeqa.selftest.base import oeSelfTest
+from oeqa.selftest.case import OESelftestTestCase
+#from oeqa.utils.decorators import testcase
+
+
+class ImportedTests(OESelftestTestCase):
+
+    def test_unconditional_pass(self):
+        """
+        Summary: Doesn't check anything, used to check import test from other layers.
+        Expected: 1. Pass unconditionally
+        Product: oe-core
+        Author: Mariano Lopez <mariano.lopez@intel.com
+        """
+
+        self.assertEqual(True, True, msg = "Impossible to fail this test")

meta/lib/oeqa/selftest/cases/selftest.py

@@ -0,0 +1,51 @@
+import importlib
+from oeqa.utils.commands import runCmd
+import oeqa.selftest
+from oeqa.selftest.case import OESelftestTestCase
+from oeqa.core.decorator.oeid import OETestID
+
+class ExternalLayer(OESelftestTestCase):
+
+    @OETestID(1885)
+    def test_list_imported(self):
+        """
+        Summary: Checks functionality to import tests from other layers.
+        Expected: 1. File "external-layer.py" must be in
+        oeqa.selftest.__path__
+                  2. test_unconditional_pas method must exists
+                     in ImportedTests class
+        Product: oe-core
+        Author: Mariano Lopez <mariano.lopez@intel.com>
+        """
+
+        test_file = "external-layer.py"
+        test_module = "oeqa.selftest.cases.external-layer"
+        method_name = "test_unconditional_pass"
+
+        # Check if "external-layer.py" is in oeqa path
+        found_file = search_test_file(test_file)
+        self.assertTrue(found_file, msg="Can't find %s in the oeqa path" % test_file)
+
+        # Import oeqa.selftest.external-layer module and search for
+        # test_unconditional_pass method of ImportedTests class
+        found_method = search_method(test_module, method_name)
+        self.assertTrue(method_name, msg="Can't find %s method" % method_name)
+
+def search_test_file(file_name):
+    for layer_path in oeqa.selftest.__path__:
+        for _, _, files in os.walk(layer_path):
+            for f in files:
+                if f == file_name:
+                    return True
+    return False
+
+def search_method(module, method):
+    modlib = importlib.import_module(module)
+    for var in vars(modlib):
+        klass = vars(modlib)[var]
+        if isinstance(klass, type(OESelftestTestCase)) and issubclass(klass, OESelftestTestCase):
+            for m in dir(klass):
+                if m == method:
+                    return True
+    return False
+