Add pytest suite and CI (roadmap A1)

37 headless tests covering the logic that is cheap to break:
- split planner: plan_disc_split, chapter helpers (whole-fit, multi-disc
  partition, single-movie chapter/even-cut split, contiguous coverage)
- High-profile fill-disc bitrate math (disc count + bounds + capacity)
- ffmpeg command generation: profiles, text/image hardsub, 2-pass, nice,
  progress-to-file, even pad/crop + positive offsets, -ss seek, and the
  AC3 448k audio-clamp regression
- ffprobe subtitle detection: text/image classification, tags/disposition

tests/conftest.py makes the in-tree package importable and installs the
gettext _ builtin so modules run headless. Forgejo Actions workflow runs
the suite on push/PR. Update CLAUDE.md's testing section accordingly.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

tests/test_ffmpeg_command.py

@@ -0,0 +1,136 @@
+"""Tests for ffmpeg.convert_file command generation (no encoding runs)."""
+
+from conftest import ffmpeg_converter, arg_after
+
+
+def _vf(cmd):
+    return arg_after(cmd, "-vf")
+
+
+def test_compatibility_dvd_basics(make_file_project):
+    conv = ffmpeg_converter(profile="compatibility")
+    conv.convert_file(make_file_project(), "/tmp/out.mpg", 0)
+    cmd = conv.command_var
+    assert "mpeg2video" in cmd
+    assert "ac3" in cmd                      # fork uses AC3 for NTSC DVD
+    assert arg_after(cmd, "-ar") == "48000"
+    assert arg_after(cmd, "-b:v") == str(4500 * 1000)
+    assert arg_after(cmd, "-b:a") == str(192 * 1000)
+    assert _vf(cmd) == "scale=720:480"
+    assert "-sn" in cmd                      # no soft-sub passthrough
+
+
+def test_runs_under_nice(make_file_project):
+    conv = ffmpeg_converter()
+    conv.convert_file(make_file_project(), "/tmp/out.mpg", 0)
+    assert conv.command_var[:4] == ["nice", "-n", "10", "ffmpeg"]
+
+
+def test_progress_goes_to_file_not_pipe(make_file_project):
+    # the deadlock fix: -progress must target a file, never pipe:N
+    conv = ffmpeg_converter()
+    conv.convert_file(make_file_project(), "/tmp/out.mpg", 0)
+    prog = arg_after(conv.command_var, "-progress")
+    assert prog is not None
+    assert not prog.startswith("pipe:")
+    assert prog.endswith(".progress")
+
+
+def test_text_hardsub_filter_after_scale(make_file_project):
+    fp = make_file_project(
+        hardsub_index=2, hardsub_kind="text",
+        embedded_subtitles=[{"index": 2, "codec": "subrip", "language": "eng",
+                             "title": "", "default": True, "forced": False,
+                             "kind": "text"}],
+    )
+    conv = ffmpeg_converter()
+    conv.convert_file(fp, "/tmp/out.mpg", 0)
+    vf = _vf(conv.command_var)
+    assert vf is not None
+    assert vf.startswith("scale=720:480")
+    assert "subtitles=" in vf
+    assert "si=0" in vf                       # first (and only) subtitle stream
+
+
+def test_text_hardsub_escapes_path(make_file_project):
+    fp = make_file_project(
+        file_name="/movies/My Movie: 2024.mkv",
+        hardsub_index=2, hardsub_kind="text",
+        embedded_subtitles=[{"index": 2, "codec": "subrip", "language": "eng",
+                             "title": "", "default": False, "forced": False,
+                             "kind": "text"}],
+    )
+    conv = ffmpeg_converter()
+    conv.convert_file(fp, "/tmp/out.mpg", 0)
+    vf = _vf(conv.command_var)
+    assert r"\:" in vf                        # the ':' in the path is escaped
+
+
+def test_image_hardsub_uses_filter_complex_overlay(make_file_project):
+    fp = make_file_project(
+        hardsub_index=3, hardsub_kind="image",
+        embedded_subtitles=[{"index": 3, "codec": "hdmv_pgs_subtitle",
+                             "language": "eng", "title": "", "default": True,
+                             "forced": False, "kind": "image"}],
+    )
+    conv = ffmpeg_converter()
+    conv.convert_file(fp, "/tmp/out.mpg", 0)
+    cmd = conv.command_var
+    fc = arg_after(cmd, "-filter_complex")
+    assert fc is not None
+    assert "overlay" in fc
+    # overlay must come before scale so bitmap subs stay aligned to the source
+    assert fc.index("overlay") < fc.index("scale=720:480")
+    assert fc.endswith("[vsub]")
+    assert arg_after(cmd, "-map") == "[vsub]"   # video taken from the graph
+    assert "-vf" not in cmd                      # not both -vf and filter_complex
+
+
+def test_high_profile_two_pass_and_448k_audio(make_file_project):
+    # regression for the AC3 448k -> 384k clamp bug
+    fp = make_file_project(two_pass_encoding=True,
+                           video_rate_final=3752, audio_rate_final=448)
+    conv = ffmpeg_converter(profile="high")
+    conv.convert_file(fp, "/tmp/out.mpg", 0)
+    cmd = conv.command_var
+    assert "-pass" in cmd and "-passlogfile" in cmd
+    assert arg_after(cmd, "-b:a") == str(448 * 1000)   # NOT clamped to 384k
+    assert arg_after(cmd, "-b:v") == str(3752 * 1000)
+    assert len(conv.childs) == 1                        # spawns the pass-2 child
+
+
+def test_audio_bitrate_table_allows_ac3_rates(make_file_project):
+    conv = ffmpeg_converter()
+    assert conv._adjust_audio_bitrate(448) == 448
+    assert conv._adjust_audio_bitrate(400) == 448      # rounds up to next valid
+    assert conv._adjust_audio_bitrate(192) == 192
+    assert conv._adjust_audio_bitrate(9999) == 640     # clamps to table max
+
+
+def test_even_dimensions_and_positive_crop_offset(make_file_project):
+    # odd letterbox height (1079) must be rounded even, offset positive
+    fp = make_file_project(width_midle=1920, height_midle=1079)
+    conv = ffmpeg_converter()
+    conv.convert_file(fp, "/tmp/out.mpg", 0)
+    cmd = conv.command_var
+    blob = _vf(cmd) or arg_after(cmd, "-filter_complex") or ""
+    assert "1079" not in blob                  # no odd dimension
+    assert ":-" not in blob                    # no negative crop/pad offset
+    assert "1078" in blob                      # rounded down to even
+
+
+def test_start_offset_emits_ss_before_inputs(make_file_project):
+    conv = ffmpeg_converter()
+    conv.convert_file(make_file_project(), "/tmp/out.mpg", 0, start_offset=120)
+    cmd = conv.command_var
+    # -ss appears before each -i (two inputs: audio-delay copy + video)
+    assert cmd.count("-ss") == 2
+    first_i = cmd.index("-i")
+    first_ss = cmd.index("-ss")
+    assert first_ss < first_i
+
+
+def test_no_start_offset_has_no_ss(make_file_project):
+    conv = ffmpeg_converter()
+    conv.convert_file(make_file_project(), "/tmp/out.mpg", 0)
+    assert "-ss" not in conv.command_var