Bash Testing

Testing frameworks and patterns for shell scripts, focusing on shunit2 and shellspec.

Framework Selection

| Framework | Strengths | Best For | | ------------- | ----------------------------- | ----------------------------- | | shunit2 | xUnit style, simple, portable | Unit tests, function testing | | shellspec | BDD style, modern, extensive | Behavior specs, full projects |

shunit2

Installation

# Download directly
curl -L https://github.com/kward/shunit2/raw/master/shunit2 -o shunit2

# Or via package manager
apt install shunit2
brew install shunit2

Basic Test Structure

#!/usr/bin/env bash

# Source the script being tested
source ./my_script.sh

# Test functions start with test
test_addition() {
    result=$(add 2 3)
    assertEquals "2 + 3 should equal 5" "5" "$result"
}

test_string_output() {
    result=$(greet "World")
    assertEquals "Hello, World" "$result"
}

test_file_creation() {
    create_temp_file
    assertTrue "Temp file should exist" "[ -f /tmp/testfile ]"
}

test_exit_code() {
    validate_input "valid"
    assertEquals "Should return 0 for valid input" 0 $?
}

# Setup and teardown
oneTimeSetUp() {
    # Run once before all tests
    export TEST_DIR=$(mktemp -d)
}

oneTimeTearDown() {
    # Run once after all tests
    rm -rf "$TEST_DIR"
}

setUp() {
    # Run before each test
    cd "$TEST_DIR"
}

tearDown() {
    # Run after each test
    rm -f "$TEST_DIR"/*
}

# Load shunit2
source shunit2

shunit2 Assertions

# Equality
assertEquals [message] expected actual
assertNotEquals [message] unexpected actual

# Null/Empty
assertNull [message] value
assertNotNull [message] value

# Boolean/Status
assertTrue [message] condition
assertFalse [message] condition

# Same reference (string comparison)
assertSame [message] expected actual
assertNotSame [message] unexpected actual

# Contains (in string)
assertContains [message] container content

# Exit status
assertEquals 0 $?

Testing Functions in Isolation

Code examples

#!/usr/bin/env bash
# test_my_functions.sh

source ./my_functions.sh

test_calculate_sum_empty() {
    result=$(calculate_sum)
    assertEquals "Empty sum should be 0" "0" "$result"
}

test_calculate_sum_single() {
    result=$(calculate_sum 5)
    assertEquals "5" "$result"
}

test_calculate_sum_multiple() {
    result=$(calculate_sum 1 2 3 4 5)
    assertEquals "15" "$result"
}

test_validate_email_valid() {
    validate_email "test@example.com"
    assertTrue "Valid email should pass" $?
}

test_validate_email_invalid() {
    validate_email "not-an-email"
    assertFalse "Invalid email should fail" $?
}

source shunit2

shellspec

Installation

# Via curl
curl -fsSL https://git.io/shellspec | sh

# Via Homebrew
brew install shellspec

# Via package managers
apt install shellspec

Directory Structure

project/
├── lib/
│   └── functions.sh
├── spec/
│   ├── spec_helper.sh
│   ├── functions_spec.sh
│   └── support/
│       └── fixtures/
└── .shellspec

Configuration (.shellspec)

--require spec_helper
--format documentation
--color

Basic Spec Structure

Code examples

shellspec Matchers

# Output matchers
The output should eq "exact match"
The output should include "partial"
The output should start with "prefix"
The output should end with "suffix"
The output should match pattern "*glob*"
The output should be blank

# Status matchers
The status should be success    # exit 0
The status should be failure    # exit non-zero
The status should eq 1          # specific code

# Variable matchers
The variable VAR should eq "value"
The variable VAR should be defined
The variable VAR should be undefined

# File matchers
The file "path" should be exist
The file "path" should be file
The file "path" should be directory
The file "path" should be readable

# Path matchers
The path "file.txt" should be exist

Mocking in shellspec

Describe 'deploy function'
  # Mock external command
  curl() {
    echo "mocked response"
    return 0
  }

  It 'calls API endpoint'
    When call deploy "server"
    The output should include "mocked response"
  End
End

Describe 'file operations'
  # Mock with function override
  Mock rm
    echo "rm called with: $*"
  End

  It 'attempts to remove file'
    When call cleanup_temp
    The output should include "rm called with"
  End
End

Spec Helper

# spec/spec_helper.sh

# Load common functions
spec_helper_precheck() {
  minimum_version "0.28.0"
}

spec_helper_loaded() {
  # Set up test environment
  export TEST_MODE=true
}

spec_helper_configure() {
  # Import project functions
  import 'lib/functions.sh'
}

Testing Patterns

Testing Exit Codes

# shunit2
test_success_exit() {
    run_command "valid_input"
    assertEquals 0 $?
}

test_error_exit() {
    run_command "invalid_input"
    assertEquals 1 $?
}

# shellspec
It 'exits 0 on success'
  When call run_command "valid_input"
  The status should eq 0
End

Testing stdout and stderr

# shunit2
test_stdout() {
    result=$(my_function 2>/dev/null)
    assertEquals "expected output" "$result"
}

test_stderr() {
    error=$(my_function 2>&1 >/dev/null)
    assertContains "$error" "error message"
}

# shellspec
It 'outputs to stdout'
  When call my_function
  The stdout should eq "expected output"
End

It 'outputs error to stderr'
  When call my_function
  The stderr should include "error message"
End

Testing with Fixtures

# Setup test fixtures
setUp() {
    TEST_DIR=$(mktemp -d)
    cat > "$TEST_DIR/config.json" <<EOF
{
    "key": "value"
}
EOF
}

tearDown() {
    rm -rf "$TEST_DIR"
}

test_config_parsing() {
    result=$(parse_config "$TEST_DIR/config.json")
    assertEquals "value" "$result"
}

Testing Interactive Functions

# Provide input via heredoc
test_interactive() {
    result=$(my_prompt <<EOF
yes
EOF
)
    assertEquals "confirmed" "$result"
}

# Or use printf
test_with_input() {
    result=$(printf 'yes\n' | my_prompt)
    assertEquals "confirmed" "$result"
}

Running Tests

# shunit2
./test_script.sh

# shellspec
shellspec                    # Run all specs
shellspec spec/file_spec.sh  # Run specific spec
shellspec --format tap       # TAP output
shellspec --jobs 4           # Parallel execution

Best Practices

1. One assertion per test when practical
2. Descriptive test names explaining what's tested
3. Isolate tests - no dependencies between tests
4. Test edge cases - empty input, special characters, large data
5. Clean up resources in tearDown
6. Mock external commands - don't test curl, test your logic
7. Test exit codes not just output