Add Docker support for Linux build testing

- Introduced a `Dockerfile` for setting up a minimal Ubuntu-based build environment with required dependencies.
- Added `docker-build.sh` script to simplify Linux build and test execution using Docker or Podman.
- Updated `DEVELOPER_GUIDE.md` with instructions for using Docker/Podman for Linux builds, including CI/CD integration examples.

Dockerfile

@@ -0,0 +1,20 @@
+# Minimal Dockerfile for building and testing kte on Linux
+# This container provides a build environment with all dependencies.
+# Mount the source tree at /kte when running the container.
+FROM ubuntu:22.04
+
+# Avoid interactive prompts during package installation
+ENV DEBIAN_FRONTEND=noninteractive
+
+# Install build dependencies
+RUN apt-get update && apt-get install -y \
+    build-essential \
+    cmake \
+    libncursesw5-dev \
+    && rm -rf /var/lib/apt/lists/*
+
+# Set working directory where source will be mounted
+WORKDIR /kte
+
+# Default command: build and run tests
+CMD ["sh", "-c", "cmake -B build -DBUILD_GUI=OFF -DBUILD_TESTS=ON && cmake --build build --target kte && cmake --build build --target kte_tests && ./build/kte_tests"]

docker-build.sh

@@ -0,0 +1,28 @@
+#!/bin/bash
+# Helper script to test Linux builds using Docker/Podman
+# This script mounts the current source tree into a Linux container,
+# builds kte in terminal-only mode, and runs the test suite.
+
+set -e
+
+# Detect whether to use docker or podman
+if command -v docker &> /dev/null; then
+    CONTAINER_CMD="docker"
+elif command -v podman &> /dev/null; then
+    CONTAINER_CMD="podman"
+else
+    echo "Error: Neither docker nor podman found in PATH"
+    exit 1
+fi
+
+IMAGE_NAME="kte-linux"
+
+# Check if image exists, if not, build it
+if ! $CONTAINER_CMD image inspect "$IMAGE_NAME" &> /dev/null; then
+    echo "Building $IMAGE_NAME image..."
+    $CONTAINER_CMD build -t "$IMAGE_NAME" .
+fi
+
+# Run the container with the current directory mounted
+echo "Running Linux build and tests..."
+$CONTAINER_CMD run --rm -v "$(pwd):/kte" "$IMAGE_NAME"

docs/DEVELOPER_GUIDE.md

@@ -292,6 +292,129 @@ Test files by category:
 **Total**: 98 tests across 22 test files. See `docs/BENCHMARKS.md` for
 performance benchmark results.
 
+### Docker/Podman for Linux Builds
+
+A minimal `Dockerfile` is provided for **testing Linux builds** without
+requiring a native Linux system. The Dockerfile creates a build
+environment container with all necessary dependencies. Your source tree
+is mounted into the container at runtime, allowing you to test
+compilation and run tests on Linux.
+
+**Important**: This is intended for testing Linux builds, not for
+running
+kte locally. The container expects the source tree to be mounted when
+run.
+
+This is particularly useful for:
+
+- **macOS/Windows developers** testing Linux compatibility
+- **CI/CD pipelines** ensuring cross-platform builds
+- **Reproducible builds** with a known Ubuntu 22.04 environment
+
+#### Prerequisites
+
+Install Docker or Podman:
+
+- **macOS**: `brew install podman` (Docker Desktop also works)
+- **Linux**: Use your distribution's package manager
+- **Windows**: Docker Desktop or Podman Desktop
+
+If using Podman on macOS, start the VM:
+
+```bash
+podman machine init
+podman machine start
+```
+
+#### Building the Docker Image
+
+The Dockerfile only installs build dependencies (g++ 11.4.0, CMake 3.22,
+libncursesw5-dev). It does not copy or build the source code.
+
+From the project root:
+
+```bash
+# Build the environment image
+docker build -t kte-linux .
+
+# Or with Podman
+podman build -t kte-linux .
+```
+
+#### Testing Linux Builds
+
+Mount your source tree and run the build + tests:
+
+```bash
+# Build and test (default command)
+docker run --rm -v "$(pwd):/kte" kte-linux
+
+# Expected output: "98 tests passed, 0 failed"
+```
+
+The default command builds kte in terminal-only mode (`-DBUILD_GUI=OFF`)
+and runs the full test suite.
+
+#### Custom Build Commands
+
+```bash
+# Open a shell in the build environment
+docker run --rm -it -v "$(pwd):/kte" kte-linux /bin/bash
+
+# Then inside the container:
+cmake -B build -DBUILD_GUI=OFF -DBUILD_TESTS=ON
+cmake --build build --target kte
+cmake --build build --target kte_tests
+./build/kte_tests
+
+# Or run kte directly
+./build/kte --help
+```
+
+#### Running kte Interactively
+
+To test kte's terminal UI on Linux:
+
+```bash
+# Run kte with a file from your host system
+docker run --rm -it -v "$(pwd):/kte" kte-linux sh -c "cmake -B build -DBUILD_GUI=OFF && cmake --build build --target kte && ./build/kte README.md"
+```
+
+#### CI/CD Integration
+
+Example GitHub Actions workflow:
+
+```yaml
+- name: Test Linux Build
+  run: |
+    docker build -t kte-linux .
+    docker run --rm -v "${{ github.workspace }}:/kte" kte-linux
+```
+
+#### Troubleshooting
+
+**"Cannot connect to Podman socket"** (macOS):
+
+```bash
+podman machine start
+```
+
+**"Permission denied"** (Linux):
+
+```bash
+# Add your user to the docker group
+sudo usermod -aG docker $USER
+# Log out and back in
+```
+
+**Build fails with ncurses errors**:
+The Dockerfile explicitly installs `libncursesw5-dev` (wide-character
+ncurses). If you modify the Dockerfile, ensure this dependency remains.
+
+**"No such file or directory" errors**:
+Ensure you're mounting the source tree with `-v "$(pwd):/kte"` when
+running the container.
+
 ### Writing Tests
 
 When adding new functionality:

tests/Test.h

@@ -57,7 +57,9 @@ template<typename A, typename B>
 inline void
 assert_eq_impl(const A &a, const B &b, const char *ea, const char *eb, const char *file, int line)
 {
-	if (!(a == b)) {
+	// Cast to common type to avoid signed/unsigned comparison warnings
+	using Common = std::common_type_t<A, B>;
+	if (!(static_cast<Common>(a) == static_cast<Common>(b))) {
 		std::ostringstream oss;
 		oss << file << ":" << line << ": ASSERT_EQ failed: " << ea << " == " << eb;
 		throw AssertionFailure{oss.str()};
@@ -72,4 +74,4 @@ assert_eq_impl(const A &a, const B &b, const char *ea, const char *eb, const cha
 
 #define EXPECT_TRUE(x) ::ktet::expect((x), #x, __FILE__, __LINE__)
 #define ASSERT_TRUE(x) ::ktet::assert_true((x), #x, __FILE__, __LINE__)
-#define ASSERT_EQ(a,b) ::ktet::assert_eq_impl((a),(b), #a, #b, __FILE__, __LINE__)
+#define ASSERT_EQ(a,b) ::ktet::assert_eq_impl((a),(b), #a, #b, __FILE__, __LINE__)

tests/test_migration_coverage.cc

@@ -424,7 +424,7 @@ TEST (Migration_SyntaxHighlighter_Pattern)
 			break; // Should never happen
 		}
 		std::string line = buf.GetLineString(row);
-		EXPECT_TRUE(line.size() >= 0); // Always true, but validates access
+		// Successfully accessed line - size() is always valid for std::string
 	}
 }