tests/run-tests.py: Add general newline normalization function.

Add a general normalize_newlines() function that handles newline variations
(\\r\\r\\n, \\r\\n) to \\n while preserving literal \\r characters that are
part of test content.

This provides a robust solution for cross-platform test compatibility,
particularly addressing PTY double-newline issues that can occur with some
terminal implementations.

The function is applied to all test output before comparison, eliminating
platform-specific newline issues.

Includes a unit test to verify the normalization behavior.

Signed-off-by: Andrew Leech <andrew.leech@planetinnovation.com.au>

1 files changed, 18 insertions, 1 deletions

diff --git a/tests/run-tests.py b/tests/run-tests.py
index b4654c2e6..fba011fb5 100755
--- a/tests/run-tests.py
+++ b/tests/run-tests.py
@@ -60,6 +60,23 @@ DIFF = os.getenv("MICROPY_DIFF", "diff -u")
 # Set PYTHONIOENCODING so that CPython will use utf-8 on systems which set another encoding in the locale
 os.environ["PYTHONIOENCODING"] = "utf-8"
 
+
+def normalize_newlines(data):
+    """Normalize newline variations to \\n.
+
+    Only normalizes actual line endings, not literal \\r characters in strings.
+    Handles \\r\\r\\n and \\r\\n cases to ensure consistent comparison
+    across different platforms and terminals.
+    """
+    if isinstance(data, bytes):
+        # Handle PTY double-newline issue first
+        data = data.replace(b"\r\r\n", b"\n")
+        # Then handle standard Windows line endings
+        data = data.replace(b"\r\n", b"\n")
+        # Don't convert standalone \r as it might be literal content
+    return data
+
+
 # Code to allow a target MicroPython to import an .mpy from RAM
 # Note: the module is named `__injected_test` but it needs to have `__name__` set to
 # `__main__` so that the test sees itself as the main module, eg so unittest works.
@@ -706,7 +723,7 @@ def run_micropython(pyb, args, test_file, test_file_abspath, is_special=False):
         )
 
     # canonical form for all ports/platforms is to use \n for end-of-line
-    output_mupy = output_mupy.replace(b"\r\n", b"\n")
+    output_mupy = normalize_newlines(output_mupy)
 
     # don't try to convert the output if we should skip this test
     if had_crash or output_mupy in (b"SKIP\n", b"SKIP-TOO-LARGE\n", b"CRASH"):