torrent.py and platform_ops.py unit tests are now all passing , moving on to integration testing

src/tests/test_torrent.py

@@ -34,8 +34,10 @@ def test_ensure_aria2c_returns_existing_executable(monkeypatch):
     installer.assert_not_called()
 
 
-def test_ensure_aria2c_returns_windows_path(monkeypatch):
+def test_ensure_aria2c_windows_returns_installed_binary(monkeypatch):
+    # Arrange
     expected = r"C:\aria2\aria2c.exe"
+    monkeypatch.setattr(torrent.sys, "platform", "win32")
 
     monkeypatch.setattr(
         torrent,
@@ -45,7 +47,8 @@ def test_ensure_aria2c_returns_windows_path(monkeypatch):
 
     assert torrent.ensure_aria2c() == expected
 
-def test_ensure_aria2c_installs_when_not_found(monkeypatch):
+def test_ensure_aria2c_windows_installs_when_binary_is_missing(monkeypatch):
+    # Arrange
     monkeypatch.setattr(
         torrent,
         "find_aria2c",
@@ -79,6 +82,7 @@ def test_ensure_aria2c_installs_when_not_found(monkeypatch):
     )
 
 def test_ensure_aria2c_linux_returns_installed_binary(monkeypatch):
+    # Arrange
     monkeypatch.setattr(
         torrent.sys,
         "platform",
@@ -105,6 +109,7 @@ def test_ensure_aria2c_linux_returns_installed_binary(monkeypatch):
     installer.assert_not_called()
 
 def test_ensure_aria2c_linux_raises_when_not_installed(monkeypatch):
+    # Arrange
     monkeypatch.setattr(
         torrent.sys,
         "platform",
@@ -134,6 +139,9 @@ def test_ensure_aria2c_linux_raises_when_not_installed(monkeypatch):
     installer.assert_not_called()
 
 def test_ensure_aria2c_passes_custom_logger(monkeypatch):
+    # Arrange
+    monkeypatch.setattr(torrent.sys, "platform", "win32")
+
     monkeypatch.setattr(
         torrent,
         "find_aria2c",
@@ -162,6 +170,9 @@ def test_ensure_aria2c_passes_custom_logger(monkeypatch):
 
 
 def test_ensure_aria2c_empty_path_triggers_install(monkeypatch):
+    # Arrange
+    monkeypatch.setattr(torrent.sys, "platform", "win32")
+
     monkeypatch.setattr(
         torrent,
         "find_aria2c",
@@ -185,6 +196,9 @@ def test_ensure_aria2c_empty_path_triggers_install(monkeypatch):
 
 
 def test_ensure_aria2c_propagates_installer_failure(monkeypatch):
+    # Arrange
+    monkeypatch.setattr(torrent.sys, "platform", "win32")
+
     monkeypatch.setattr(
         torrent,
         "find_aria2c",

src/torrent.py

@@ -29,18 +29,18 @@ _NO_WINDOW = getattr(subprocess, "CREATE_NO_WINDOW", 0)
 def ensure_aria2c(log_fn=log) -> str:
     """Return the path to aria2c.exe, downloading + checksum-verifying it into
     APP_DATA_DIR on first use. Raises on failure."""
-    ARIA2C_PATH = find_aria2c() 
+    ARIA2C_PATH = find_aria2c() # NOTE: Returns a path to a aria2c executable , otherwise this var is None  
     
-    if ARIA2C_PATH: 
+    if ARIA2C_PATH:  # NOTE: If result from find_aria2c() isn't None , returns path 
         return ARIA2C_PATH
 
    
-    if sys.platform.startswith == "win": 
+    if sys.platform.startswith("win"): # NOTE: Checks if platform is windows 
         return install_aria2c_windows( APP_DATA_DIR=APP_DATA_DIR,
                                                ALLOWED_DOWNLOAD_HOSTS=ALLOWED_DOWNLOAD_HOSTS,
                                                log_fn=log_fn)
 
-    raise RuntimeError("aria2c required but not installed")
+    raise RuntimeError("aria2c required but not installed") # NOTE: If neither windows or linux path is returned , throws runtime error  
 
 
 def _bdecode(buf: bytes, pos: int = 0):