# macOS with Homebrew
brew install bats-core
 
# Ubuntu/Debian
git clone https://github.com/bats-core/bats-core.git
cd bats-core
./install.sh /usr/local
 
# From npm (Node.js)
npm install --global bats
 
# Verify installation
bats --version

project/
├── bin/
│   ├── script.sh
│   └── helper.sh
├── tests/
│   ├── test_script.bats
│   ├── test_helper.sh
│   ├── fixtures/
│   │   ├── input.txt
│   │   └── expected_output.txt
│   └── helpers/
│       └── mocks.bash
└── README.md

#!/usr/bin/env bats
 
# Load test helper if present
load test_helper
 
# Setup runs before each test
setup() {
    export TMPDIR=$(mktemp -d)
}
 
# Teardown runs after each test
teardown() {
    rm -rf "$TMPDIR"
}
 
# Test: simple assertion
@test "Function returns 0 on success" {
    run my_function "input"
    [ "$status" -eq 0 ]
}
 
# Test: output verification
@test "Function outputs correct result" {
    run my_function "test"
    [ "$output" = "expected output" ]
}
 
# Test: error handling
@test "Function returns 1 on missing argument" {
    run my_function
    [ "$status" -eq 1 ]
}

#!/usr/bin/env bats
 
@test "Command succeeds" {
    run true
    [ "$status" -eq 0 ]
}
 
@test "Command fails as expected" {
    run false
    [ "$status" -ne 0 ]
}
 
@test "Command returns specific exit code" {
    run my_function --invalid
    [ "$status" -eq 127 ]
}
 
@test "Can capture command result" {
    run echo "hello"
    [ $status -eq 0 ]
    [ "$output" = "hello" ]
}

#!/usr/bin/env bats
 
@test "Output matches string" {
    result=$(echo "hello world")
    [ "$result" = "hello world" ]
}
 
@test "Output contains substring" {
    result=$(echo "hello world")
    [[ "$result" == *"world"* ]]
}
 
@test "Output matches pattern" {
    result=$(date +%Y)
    [[ "$result" =~ ^[0-9]{4}$ ]]
}
 
@test "Multi-line output" {
    run printf "line1\nline2\nline3"
    [ "$output" = "line1
line2
line3" ]
}
 
@test "Lines variable contains output" {
    run printf "line1\nline2\nline3"
    [ "${lines[0]}" = "line1" ]
    [ "${lines[1]}" = "line2" ]
    [ "${lines[2]}" = "line3" ]
}

#!/usr/bin/env bats
 
@test "File is created" {
    [ ! -f "$TMPDIR/output.txt" ]
    my_function > "$TMPDIR/output.txt"
    [ -f "$TMPDIR/output.txt" ]
}
 
@test "File contents match expected" {
    my_function > "$TMPDIR/output.txt"
    [ "$(cat "$TMPDIR/output.txt")" = "expected content" ]
}
 
@test "File is readable" {
    touch "$TMPDIR/test.txt"
    [ -r "$TMPDIR/test.txt" ]
}
 
@test "File has correct permissions" {
    touch "$TMPDIR/test.txt"
    chmod 644 "$TMPDIR/test.txt"
    [ "$(stat -f %OLp "$TMPDIR/test.txt")" = "644" ]
}
 
@test "File size is correct" {
    echo -n "12345" > "$TMPDIR/test.txt"
    [ "$(wc -c < "$TMPDIR/test.txt")" -eq 5 ]
}

#!/usr/bin/env bats
 
setup() {
    # Create test directory
    TEST_DIR=$(mktemp -d)
    export TEST_DIR
 
    # Source script under test
    source "${BATS_TEST_DIRNAME}/../bin/script.sh"
}
 
teardown() {
    # Clean up temporary directory
    rm -rf "$TEST_DIR"
}
 
@test "Test using TEST_DIR" {
    touch "$TEST_DIR/file.txt"
    [ -f "$TEST_DIR/file.txt" ]
}

#!/usr/bin/env bats
 
setup() {
    # Create directory structure
    mkdir -p "$TMPDIR/data/input"
    mkdir -p "$TMPDIR/data/output"
 
    # Create test fixtures
    echo "line1" > "$TMPDIR/data/input/file1.txt"
    echo "line2" > "$TMPDIR/data/input/file2.txt"
 
    # Initialize environment
    export DATA_DIR="$TMPDIR/data"
    export INPUT_DIR="$DATA_DIR/input"
    export OUTPUT_DIR="$DATA_DIR/output"
}
 
teardown() {
    rm -rf "$TMPDIR/data"
}
 
@test "Processes input files" {
    run my_process_script "$INPUT_DIR" "$OUTPUT_DIR"
    [ "$status" -eq 0 ]
    [ -f "$OUTPUT_DIR/file1.txt" ]
}

#!/usr/bin/env bats
 
# Load shared setup from test_helper.sh
load test_helper
 
# setup_file runs once before all tests
setup_file() {
    export SHARED_RESOURCE=$(mktemp -d)
    echo "Expensive setup" > "$SHARED_RESOURCE/data.txt"
}
 
# teardown_file runs once after all tests
teardown_file() {
    rm -rf "$SHARED_RESOURCE"
}
 
@test "First test uses shared resource" {
    [ -f "$SHARED_RESOURCE/data.txt" ]
}
 
@test "Second test uses shared resource" {
    [ -d "$SHARED_RESOURCE" ]
}

#!/usr/bin/env bats
 
# Mock external command
my_external_tool() {
    echo "mocked output"
    return 0
}
 
@test "Function uses mocked tool" {
    export -f my_external_tool
    run my_function
    [[ "$output" == *"mocked output"* ]]
}

#!/usr/bin/env bats
 
setup() {
    # Create stub directory
    STUBS_DIR="$TMPDIR/stubs"
    mkdir -p "$STUBS_DIR"
 
    # Add to PATH
    export PATH="$STUBS_DIR:$PATH"
}
 
create_stub() {
    local cmd="$1"
    local output="$2"
    local code="${3:-0}"
 
    cat > "$STUBS_DIR/$cmd" <<EOF
#!/bin/bash
echo "$output"
exit $code
EOF
    chmod +x "$STUBS_DIR/$cmd"
}
 
@test "Function works with stubbed curl" {
    create_stub curl "{ \"status\": \"ok\" }" 0
    run my_api_function
    [ "$status" -eq 0 ]
}

#!/usr/bin/env bats
 
@test "Function handles environment override" {
    export MY_SETTING="override_value"
    run my_function
    [ "$status" -eq 0 ]
    [[ "$output" == *"override_value"* ]]
}
 
@test "Function uses default when var unset" {
    unset MY_SETTING
    run my_function
    [ "$status" -eq 0 ]
    [[ "$output" == *"default"* ]]
}

#!/usr/bin/env bats
 
# Fixture directory: tests/fixtures/
 
setup() {
    FIXTURES_DIR="${BATS_TEST_DIRNAME}/fixtures"
    WORK_DIR=$(mktemp -d)
    export WORK_DIR
}
 
teardown() {
    rm -rf "$WORK_DIR"
}
 
@test "Process fixture file" {
    # Copy fixture to work directory
    cp "$FIXTURES_DIR/input.txt" "$WORK_DIR/input.txt"
 
    # Run function
    run my_process_function "$WORK_DIR/input.txt"
 
    # Compare output
    diff "$WORK_DIR/output.txt" "$FIXTURES_DIR/expected_output.txt"
}

#!/usr/bin/env bats
 
generate_fixture() {
    local lines="$1"
    local file="$2"
 
    for i in $(seq 1 "$lines"); do
        echo "Line $i content" >> "$file"
    done
}
 
@test "Handle large input file" {
    generate_fixture 1000 "$TMPDIR/large.txt"
    run my_function "$TMPDIR/large.txt"
    [ "$status" -eq 0 ]
    [ "$(wc -l < "$TMPDIR/large.txt")" -eq 1000 ]
}

#!/usr/bin/env bats
 
@test "Function fails with missing file" {
    run my_function "/nonexistent/file.txt"
    [ "$status" -ne 0 ]
    [[ "$output" == *"not found"* ]]
}
 
@test "Function fails with invalid input" {
    run my_function ""
    [ "$status" -ne 0 ]
}
 
@test "Function fails with permission denied" {
    touch "$TMPDIR/readonly.txt"
    chmod 000 "$TMPDIR/readonly.txt"
    run my_function "$TMPDIR/readonly.txt"
    [ "$status" -ne 0 ]
    chmod 644 "$TMPDIR/readonly.txt"  # Cleanup
}
 
@test "Function provides helpful error message" {
    run my_function --invalid-option
    [ "$status" -ne 0 ]
    [[ "$output" == *"Usage:"* ]]
}

#!/usr/bin/env bats
 
setup() {
    # Check for required tools
    if ! command -v jq &>/dev/null; then
        skip "jq is not installed"
    fi
 
    export SCRIPT="${BATS_TEST_DIRNAME}/../bin/script.sh"
}
 
@test "JSON parsing works" {
    skip_if ! command -v jq &>/dev/null
    run my_json_parser '{"key": "value"}'
    [ "$status" -eq 0 ]
}

#!/usr/bin/env bats
 
@test "Script works in bash" {
    bash "${BATS_TEST_DIRNAME}/../bin/script.sh" arg1
}
 
@test "Script works in sh (POSIX)" {
    sh "${BATS_TEST_DIRNAME}/../bin/script.sh" arg1
}
 
@test "Script works in dash" {
    if command -v dash &>/dev/null; then
        dash "${BATS_TEST_DIRNAME}/../bin/script.sh" arg1
    else
        skip "dash not installed"
    fi
}

#!/usr/bin/env bats
 
@test "Multiple independent operations" {
    run bash -c 'for i in {1..10}; do
        my_operation "$i" &
    done
    wait'
    [ "$status" -eq 0 ]
}
 
@test "Concurrent file operations" {
    for i in {1..5}; do
        my_function "$TMPDIR/file$i" &
    done
    wait
    [ -f "$TMPDIR/file1" ]
    [ -f "$TMPDIR/file5" ]
}

#!/usr/bin/env bash
 
# Source script under test
export SCRIPT_DIR="${BATS_TEST_DIRNAME%/*}/bin"
 
# Common test utilities
assert_file_exists() {
    if [ ! -f "$1" ]; then
        echo "Expected file to exist: $1"
        return 1
    fi
}
 
assert_file_equals() {
    local file="$1"
    local expected="$2"
 
    if [ ! -f "$file" ]; then
        echo "File does not exist: $file"
        return 1
    fi
 
    local actual=$(cat "$file")
    if [ "$actual" != "$expected" ]; then
        echo "File contents do not match"
        echo "Expected: $expected"
        echo "Actual: $actual"
        return 1
    fi
}
 
# Create temporary test directory
setup_test_dir() {
    export TEST_DIR=$(mktemp -d)
}
 
cleanup_test_dir() {
    rm -rf "$TEST_DIR"
}

name: Tests
 
on: [push, pull_request]
 
jobs:
  test:
    runs-on: ubuntu-latest
 
    steps:
      - uses: actions/checkout@v3
 
      - name: Install Bats
        run: |
          npm install --global bats
 
      - name: Run Tests
        run: |
          bats tests/*.bats
 
      - name: Run Tests with Tap Reporter
        run: |
          bats tests/*.bats --tap | tee test_output.tap

.PHONY: test test-verbose test-tap
 
test:
	bats tests/*.bats
 
test-verbose:
	bats tests/*.bats --verbose
 
test-tap:
	bats tests/*.bats --tap
 
test-parallel:
	bats tests/*.bats --parallel 4
 
coverage: test
	# Optional: Generate coverage reports