Does this skill work with shells other than Bash?

Yes. The skill includes patterns for testing across Bash, POSIX sh, and dash, with examples showing how to skip tests gracefully when a shell dialect is unavailable.

Can I run Bats tests in parallel?

Yes. The skill shows parallel execution patterns and includes Makefile examples with a `test-parallel` target that runs tests with a concurrency limit.

Does this integrate with CI/CD?

Yes. The skill includes GitHub Actions workflow examples and Makefile patterns for running Bats tests in pipelines, with support for TAP reporter output.

How do I test shell scripts that depend on external tools?

The skill provides setup patterns that check for required dependencies and skip tests when they are missing, plus examples of mocking and isolating units under test.

What testing patterns does this cover?

The skill covers error condition testing, dependency handling, shell compatibility validation, test helpers, fixtures, and parallel execution, with worked examples for each.

bats-testing-patterns by wshobson

bats-testing-patterns — detailed patterns and worked examples

Bats Fundamentals

What is Bats?

Bats (Bash Automated Testing System) is a TAP (Test Anything Protocol) compliant testing framework for shell scripts that provides:

Simple, natural test syntax
TAP output format compatible with CI systems
Fixtures and setup/teardown support
Assertion helpers
Parallel test execution

Installation

# 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

File Structure

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

Basic Test Structure

Simple Test File

#!/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 ]
}

Assertion Patterns

Exit Code Assertions

#!/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" ]
}

Output Assertions

#!/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" ]
}

File Assertions

#!/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 ]
}

Setup and Teardown Patterns

Basic Setup and Teardown

#!/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" ]
}

Setup with Resources

#!/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" ]
}

Global Setup/Teardown

#!/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" ]
}

Mocking and Stubbing Patterns

Function Mocking

#!/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"* ]]
}

Command Stubbing

#!/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 ]
}

Variable Stubbing

#!/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"* ]]
}

Fixture Management

Using Fixture Files

#!/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"
}

Dynamic Fixture Generation

#!/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 ]
}

/bats-testing-patterns

referencesdetails.md

bats-testing-patterns — detailed patterns and worked examples

Bats Fundamentals

What is Bats?

Installation

File Structure

Basic Test Structure

Simple Test File

Assertion Patterns

Exit Code Assertions

Output Assertions

File Assertions

Setup and Teardown Patterns

Basic Setup and Teardown

Setup with Resources

Global Setup/Teardown

Mocking and Stubbing Patterns

Function Mocking

Command Stubbing

Variable Stubbing

Fixture Management

Using Fixture Files

Dynamic Fixture Generation

Advanced Patterns

Third-party checks

Provenance

Topics

What it does

Frequently asked

/bats-testing-patterns

bats-testing-patternsreferencesdetails.md

bats-testing-patterns — detailed patterns and worked examples

Bats Fundamentals

What is Bats?

Installation

File Structure

Basic Test Structure

Simple Test File

Assertion Patterns

Exit Code Assertions

Output Assertions

File Assertions

Setup and Teardown Patterns

Basic Setup and Teardown

Setup with Resources

Global Setup/Teardown

Mocking and Stubbing Patterns

Function Mocking

Command Stubbing

Variable Stubbing

Fixture Management

Using Fixture Files

Dynamic Fixture Generation

Advanced Patterns

Third-party checks

Provenance

Topics

README badge

What it does

Frequently asked

Related skills

referencesdetails.md