tests: Run test.py with full logging in the presence of TEST_LOGS environment variable

test.py

@@ -846,6 +846,11 @@ def make_paths():
 VALGRIND_SUPPRESSIONS_FILE = ".ns3.supp"
 # VALGRIND_SUPPRESSIONS_FILE = None
 
+# When the TEST_LOGS environment variable is set to 1 or true,
+# NS_LOG is set to NS_LOG=*, and stdout/stderr
+# from tests are discarded to prevent running out of memory.
+TEST_LOGS = bool(os.getenv("TEST_LOGS", False))
+
 
 def run_job_synchronously(shell_command, directory, valgrind, is_python, build_path=""):
     if VALGRIND_SUPPRESSIONS_FILE is not None:
@@ -878,9 +883,16 @@ def run_job_synchronously(shell_command, directory, valgrind, is_python, build_p
 
     start_time = time.time()
     proc = subprocess.Popen(
-        cmd, shell=True, cwd=directory, stdout=subprocess.PIPE, stderr=subprocess.PIPE
+        cmd,
+        shell=True,
+        cwd=directory,
+        stdout=subprocess.PIPE if not TEST_LOGS else subprocess.DEVNULL,
+        stderr=subprocess.PIPE if not TEST_LOGS else subprocess.STDOUT,
     )
     stdout_results, stderr_results = proc.communicate()
+    stdout_results = b"" if stdout_results is None else stdout_results
+    stderr_results = b"" if stderr_results is None else stderr_results
+
     elapsed_time = time.time() - start_time
 
     retval = proc.returncode
@@ -1343,7 +1355,7 @@ def run_tests():
     # test.py runs.  If you want to see logging output from your tests, you
     # have to run them using the test-runner directly.
     #
-    os.environ["NS_LOG"] = ""
+    os.environ["NS_LOG"] = "*" if TEST_LOGS else ""
 
     #
     # There are a couple of options that imply we can to exit before starting