mosaic

Testing Guide

This guide covers local testing, mock-based tests, integration tests, and smoke tests.

Fast Test Suite

go test ./...

If the default Go build cache is not writable:

GOCACHE=/tmp/go-build go test ./...

Vet

GOCACHE=/tmp/go-build go vet ./...

Coverage

GOCACHE=/tmp/go-build go test ./... -cover

Lint

golangci-lint run

Run lint before commits when golangci-lint is installed.

Test Categories

Unit Tests

Unit tests cover:

• FFprobe JSON parsing.
• FPS parsing.
• Orientation metadata parsing.
• Rotation filter selection.
• Ladder generation.
• Bitrate optimization.
• HLS filter graph generation.
• DASH and HLS FFmpeg argument construction.
• Progress parsing.
• Executor behavior.

Mocked Command Tests

Most encode tests use a fake executor.CommandExecutor.

This avoids:

• requiring FFmpeg in every unit test
• network access
• slow media processing
• fixture media files

Integration-Style Tests

Some tests replace executor.DefaultExecutor with a mock and exercise public wrappers.

Real FFmpeg and FFprobe smoke tests are best run manually because they depend on installed binaries and fixture media.

Smoke Test: Local File

Create a short input:

ffmpeg -y \
  -f lavfi -i testsrc2=size=1080x1080:duration=3 \
  -c:v libx264 \
  /tmp/mosaic-square.mp4

Run a small Go program:

package main

import (
	"context"
	"log"

	"github.com/farshidrezaei/mosaic"
)

func main() {
	_, err := mosaic.EncodeHls(
		context.Background(),
		mosaic.Job{
			Input:     "/tmp/mosaic-square.mp4",
			OutputDir: "/tmp/mosaic-square-hls",
			Profile:   mosaic.ProfileVOD,
		},
		mosaic.WithNormalizeOrientation(),
	)
	if err != nil {
		log.Fatal(err)
	}
}

Validate dimensions:

for f in /tmp/mosaic-square-hls/init*.mp4; do
  echo "$f"
  ffprobe -v error -select_streams v:0 \
    -show_entries stream=width,height:stream_tags=rotate:stream_side_data=rotation \
    -of csv=p=0 "$f"
done

Expected dimensions for 1080x1080:

1080,1080
720,720
360,360

Smoke Test: Rotated Portrait

Use a video with stored landscape dimensions and -90 display rotation.

Expected behavior:

• Output is portrait.
• Rotation metadata is cleared.
• Frame is not upside down.
• Aspect ratio is preserved.

Example expected dimensions for display 1080x1920:

608,1080
404,720
202,360

Smoke Test: Remote URL

Remote inputs require FFmpeg and FFprobe network access.

job := mosaic.Job{
	Input:     "https://example.com/video.mp4",
	OutputDir: "/tmp/mosaic-url-hls",
	Profile:   mosaic.ProfileVOD,
}
_, err := mosaic.EncodeHls(context.Background(), job, mosaic.WithNormalizeOrientation())

If DNS or network is blocked, FFprobe fails before encoding:

Failed to resolve hostname
Input/output error

Inspecting Output

List files:

find /tmp/mosaic-output -maxdepth 1 -type f -printf '%f\n' | sort

Probe an init segment:

ffprobe -v error -select_streams v:0 \
  -show_entries stream=width,height,avg_frame_rate:stream_tags=rotate:stream_side_data=rotation \
  -of json /tmp/mosaic-output/init_0.mp4

Extract a frame:

ffmpeg -y -ss 2 -i /tmp/mosaic-output/stream_0.m3u8 \
  -frames:v 1 /tmp/mosaic-frame.png

Common Test Environment Issue

If tests fail with:

read-only file system

set GOCACHE to a writable directory:

GOCACHE=/tmp/go-build go test ./...

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