# Testbox Mockbox > Use this skill when creating mocks, stubs, and spies in TestBox using MockBox: createMock(), createEmptyMock(), prepareMock(), stubbing methods with $(), chaining $args()/$results()/$throws(), verifying call counts with $once()/$never()/$times()/$atLeast()/$atMost(), reading call logs with $callLog(), injecting mock properties with $property(), simulating queries with querySim(), or spying on real methods with $spy(). - Skill: `coldbox/testbox-mockbox` (Agent Skill) - Install (CLI): `npx skillmds@latest add coldbox/testbox-mockbox` - Raw SKILL.md: https://api.skillmd.com/api/skills/coldbox/testbox-mockbox/raw - Safety review: pending - Works with: Claude Code, Claude.ai, OpenAI Codex - Category: Coding & Dev Tools - Author: ColdBox (https://skillmd.com/u/coldbox) - Updated: 2026-09-17 - Page: https://skillmd.com/skills/coldbox/testbox-mockbox --- # MockBox — Mocking & Stubbing in TestBox ## When to Use This Skill - Replacing real dependencies (DAOs, APIs, email services) with controlled test doubles - Stubbing method return values for different arguments - Verifying how many times a method was called and with what arguments - Making a method throw a specific exception - Spying on internal private methods of the object under test - Injecting mock property values directly into objects --- ## Creating Test Doubles ```boxlang // Full mock — real class instantiated, all methods can be stubbed variables.mockUserService = createMock( "models.UserService" ) // Full mock from an already-instantiated object variables.mockUserService = createMock( object: new models.UserService() ) // Empty mock — all methods wiped; you must stub every method used variables.mockDAO = createEmptyMock( "models.UserDAO" ) // Partial mock — decorate a real object; unstubbed methods execute normally variables.spySecurity = prepareMock( new models.SecurityService() ) ``` | Factory | Methods kept? | Use case | |---|---|---| | `createMock()` | Yes (stubbable) | Replace collaborator dependencies | | `createEmptyMock()` | No (all wiped) | Mock an interface or abstract base | | `prepareMock()` | Yes (targeted stubs only) | Spy on internal private methods | --- ## Stubbing Return Values — `$()` ```boxlang // Return a fixed value every call mockDAO.$( "findById" ).$results( { id: 1, name: "Alice" } ) // Shorthand: inline returns mockDAO.$( "findById", { id: 1, name: "Alice" } ) // Multiple sequential results (cycles on last after exhausting) mockDAO.$( "getNextRecord" ).$results( { id: 1 }, { id: 2 }, { id: 3 } ) // call1 → {id:1}, call2 → {id:2}, call3+ → {id:3} // Chain multiple stubs on one mock mockService.$( "isFound", false ).$( "isDirty", false ).$( "isSaved", true ) // Dynamic result via callback (receives caller arguments as array) mockCalc.$( "calculate", ( args ) => args[ 1 ] * 2 ) // Void method (returns nothing, just track calls) mockEmailService.$( "send" ) ``` --- ## Argument-Specific Stubs — `$args()` When the same method is called with **different arguments** and must return different values: ```boxlang // Positional mockConfig.$( "getKey" ) .$args( "debugMode" ).$results( true ) .$args( "outgoingMail" ).$results( "dev@example.com" ) // Named mockConfig.$( "getKey" ) .$args( name: "debugMode" ).$results( true ) .$args( name: "outgoingMail" ).$results( "dev@example.com" ) // Usage expect( mockConfig.getKey( "debugMode" ) ).toBeTrue() expect( mockConfig.getKey( "outgoingMail" ) ).toBe( "dev@example.com" ) ``` > Always follow `$args()` with `$results()`. --- ## Throwing Exceptions — `$throws()` ```boxlang // Chain approach mockDAO.$( "delete" ) .$args( id: 999 ) .$throws( type: "NotFoundException", message: "Record 999 not found" ) // Inline approach mockDAO.$( method: "delete", throwException: true, throwType: "NotFoundException", throwMessage: "Record not found", throwDetail: "id=999", throwErrorCode: "404" ) // Confirm in spec expect( () => service.delete( 999 ) ).toThrow( type: "NotFoundException" ) ``` --- ## Injecting Properties — `$property()` Inject a mock directly into any scope of the SUT without needing a setter: ```boxlang prepareMock( variables.sut ) .$property( propertyName: "userRepository", propertyScope: "variables", // default mock: mockUserRepository ) // Read it back var injected = variables.sut.$getProperty( "userRepository" ) ``` --- ## Query Simulation — `querySim()` Build query objects inline using pipe-delimited syntax: ```boxlang var userQuery = querySim( "id, name, email 1 | Alice Majano | alice@example.com 2 | Bob Clapton | bob@example.com 3 | Carol Degeneres| carol@example.com" ) mockDAO.$( "findAll" ).$results( userQuery ) var result = userService.listAll() expect( result.recordCount ).toBe( 3 ) expect( result.name[ 1 ] ).toBe( "Alice Majano" ) ``` --- ## Spying on Real Methods — `$spy()` The real implementation still executes; MockBox logs calls so you can verify them: ```boxlang prepareMock( variables.sut ) variables.sut.$spy( "sendWelcomeEmail" ) userService.register( { name: "Alice", email: "alice@example.com" } ) expect( variables.sut.$once( "sendWelcomeEmail" ) ).toBeTrue() ``` --- ## Verification Methods ```boxlang // Exactly once expect( mockEmailService.$once( "send" ) ).toBeTrue() // Never called expect( mockAuditService.$never( "logError" ) ).toBeTrue() // Exactly N times expect( mockDAO.$times( 3, "findById" ) ).toBeTrue() expect( mockDAO.$verifyCallCount( 3, "findById" ) ).toBeTrue() // alias // At least N (>= N) expect( mockDAO.$atLeast( 2, "findById" ) ).toBeTrue() // At most N (<= N) expect( mockDAO.$atMost( 5, "save" ) ).toBeTrue() // Raw count var total = mockDAO.$count() // all methods var saveCount = mockDAO.$count( "save" ) // specific method ``` --- ## Inspecting Call Logs — `$callLog()` `$callLog()` returns a struct keyed by method name; each value is an array of argument structs. ```boxlang mockSession.$( "setVar", callLogging: true ) mockSession.setVar( "Hello", "World" ) mockSession.setVar( "Name", "Alice" ) var logs = mockSession.$callLog() // logs.setVar is an array of 2 ordered argument structs expect( logs.setVar ).toHaveLength( 2 ) expect( logs.setVar[ 1 ][ "1" ] ).toBe( "Hello" ) // positional key "1" expect( logs.setVar[ 2 ][ "1" ] ).toBe( "Name" ) ``` --- ## Resetting Between Specs ```boxlang afterEach( () => { mockDAO.$reset() // clears $count, $callLog, all stubs remain mockEmailService.$reset() } ) ``` --- ## Complete Integration Example ```boxlang class extends="testbox.system.BaseSpec" { function beforeAll() { variables.mockUserDAO = createEmptyMock( "models.UserDAO" ) variables.mockEmailService = createEmptyMock( "models.EmailService" ) variables.sut = prepareMock( new models.UserService() ) .$property( propertyName: "userDAO", mock: mockUserDAO ) .$property( propertyName: "emailService", mock: mockEmailService ) } function run() { describe( "UserService.register()", () => { beforeEach( () => { mockUserDAO.$reset() mockEmailService.$reset() } ) it( "saves user and sends welcome email", () => { mockUserDAO.$( "save" ).$results( { id: 1, name: "Alice" } ) mockEmailService.$( "sendWelcome" ) var result = sut.register( { name: "Alice", email: "alice@example.com" } ) expect( result.id ).toBe( 1 ) expect( mockUserDAO.$once( "save" ) ).toBeTrue() expect( mockEmailService.$once( "sendWelcome" ) ).toBeTrue() } ) it( "does not send email when save fails", () => { mockUserDAO.$( "save" ) .$throws( type: "DatabaseException", message: "Duplicate entry" ) expect( () => sut.register( { name: "Dup", email: "dup@example.com" } ) ) .toThrow( type: "DatabaseException" ) expect( mockEmailService.$never( "sendWelcome" ) ).toBeTrue() } ) it( "calls save with the correct data arguments", () => { mockUserDAO.$( "save", callLogging: true ).$results( { id: 2 } ) mockEmailService.$( "sendWelcome" ) sut.register( { name: "Bob", email: "bob@example.com" } ) var log = mockUserDAO.$callLog() expect( log.save[ 1 ] ).toHaveKey( "name" ) expect( log.save[ 1 ].name ).toBe( "Bob" ) } ) } ) } } ``` --- ## Quick Reference | Method | Returns | Description | |---|---|---| | `createMock( className\|object )` | mock | Full mock, methods intact | | `createEmptyMock( className\|object )` | mock | All methods wiped | | `prepareMock( object )` | mock | Decorate existing instance | | `mock.$( method, [returns] )` | mock | Stub a method | | `mock.$args( ...args )` | mock | Match specific call arguments | | `mock.$results( ...values )` | mock | Set sequential return values | | `mock.$throws( type, message, detail )` | mock | Make method throw | | `mock.$property( name, scope, mock )` | mock | Inject into any scope | | `mock.$getProperty( name, [scope] )` | any | Read internal property | | `mock.$spy( method )` | mock | Spy on real method (real runs + log) | | `querySim( dsv )` | query | Build query from pipe-delimited string | | `mock.$once( [method] )` | boolean | Called exactly once | | `mock.$never( [method] )` | boolean | Never called | | `mock.$times( n, [method] )` | boolean | Called exactly N times | | `mock.$atLeast( n, [method] )` | boolean | Called >= N times | | `mock.$atMost( n, [method] )` | boolean | Called <= N times | | `mock.$count( [method] )` | numeric | Call count | | `mock.$callLog()` | struct | All call argument logs | | `mock.$reset()` | void | Reset counters and logs | | `mock.$debug()` | struct | Debugging info |