[3/3] arm/selftest: add test that DISPLAY is forwarded into the runfvp child

diff --git a/meta-arm/lib/oeqa/selftest/cases/runfvp.py b/meta-arm/lib/oeqa/selftest/cases/runfvp.py
index 61ce2ab9..c995f89e 100644
--- a/meta-arm/lib/oeqa/selftest/cases/runfvp.py
+++ b/meta-arm/lib/oeqa/selftest/cases/runfvp.py
@@ -1,4 +1,3 @@ 
-import asyncio
 import os
 import json
 import pathlib
@@ -17,7 +16,7 @@  class RunFVPTests(OESelftestTestCase):
     def setUpLocal(self):
         self.assertTrue(runfvp.exists())
 
-    def run_fvp(self, *args, should_succeed=True):
+    def run_fvp(self, *args, env=None, should_succeed=True):
         """
         Call runfvp passing any arguments. If check is True verify return stdout
         on exit code 0 or fail the test, otherwise return the CompletedProcess
@@ -26,7 +25,7 @@  class RunFVPTests(OESelftestTestCase):
         cli = [runfvp,] + list(args)
         print(f"Calling {cli}")
         # Set cwd to testdir so that any mock FVPs are found
-        ret = subprocess.run(cli, cwd=testdir, stdout=subprocess.PIPE, stderr=subprocess.STDOUT, universal_newlines=True)
+        ret = subprocess.run(cli, cwd=testdir, env=env, stdout=subprocess.PIPE, stderr=subprocess.STDOUT, universal_newlines=True)
         if should_succeed:
             self.assertEqual(ret.returncode, 0, f"runfvp exit {ret.returncode}, output: {ret.stdout}")
             return ret.stdout
@@ -53,6 +52,10 @@  class RunFVPTests(OESelftestTestCase):
         # test-parameter sets one argument, add another manually
         self.run_fvp(testdir / "test-parameter.json", "--", "--parameter", "board.dog=woof")
 
+    def test_fvp_environment(self):
+        output = self.run_fvp(testdir / "test-environment.json", env={"DISPLAY": "test_fvp_environment:42"})
+        self.assertEqual(output.strip(), "Found expected DISPLAY")
+
 @OETestTag("meta-arm")
 class ConfFileTests(OESelftestTestCase):
     def test_no_exe(self):
diff --git a/meta-arm/lib/oeqa/selftest/cases/tests/mock-fvp.py b/meta-arm/lib/oeqa/selftest/cases/tests/mock-fvp.py
index 2213c9f0..6cf8e454 100755
--- a/meta-arm/lib/oeqa/selftest/cases/tests/mock-fvp.py
+++ b/meta-arm/lib/oeqa/selftest/cases/tests/mock-fvp.py
@@ -2,12 +2,19 @@ 
 
 import argparse
 import sys
+import os
 
 def do_test_parameters(args):
     if not args.parameter or set(args.parameter) != set(("board.cow=moo", "board.dog=woof")):
         print(f"Unexpected arguments: {args}")
         sys.exit(1)
 
+def do_test_environment(args):
+    if os.environ.get("DISPLAY") == "test_fvp_environment:42":
+        print("Found expected DISPLAY")
+    else:
+        print("Got unexpected environment %s" % str(os.environ))
+        sys.exit(1)
 
 if __name__ == "__main__":
     parser = argparse.ArgumentParser()
diff --git a/meta-arm/lib/oeqa/selftest/cases/tests/test-environment.json b/meta-arm/lib/oeqa/selftest/cases/tests/test-environment.json
new file mode 100644
index 00000000..6e23855b
--- /dev/null
+++ b/meta-arm/lib/oeqa/selftest/cases/tests/test-environment.json
@@ -0,0 +1,4 @@ 
+{
+    "fvp-bindir": ".",
+    "exe": "test-environment.py"
+}
diff --git a/meta-arm/lib/oeqa/selftest/cases/tests/test-environment.py b/meta-arm/lib/oeqa/selftest/cases/tests/test-environment.py
new file mode 120000
index 00000000..c734eeca
--- /dev/null
+++ b/meta-arm/lib/oeqa/selftest/cases/tests/test-environment.py
@@ -0,0 +1 @@ 
+mock-fvp.py
\ No newline at end of file