TestLang++
A compiler-driven DSL for fast, consistent HTTP API test generation.
Technologies Used
Problem
API tests can become repetitive and inconsistent when every endpoint test is manually coded in Java. Teams lose time on boilerplate setup and debugging brittle test files.
Solution
TestLang++ introduces a concise test language where developers write readable .test files that compile to JUnit 5 classes. The generated tests use HttpClient and assertion patterns that are reliable and easy to maintain.
Results and Impact
- Reduced repetitive test setup by expressing requests and assertions declaratively.
- Improved reliability through typed declarations and semantic validation in the compiler pipeline.
- Increased debugging speed using line-numbered diagnostics for parser and semantic errors.
Key Features
Declarative Test Syntax
Write HTTP tests in simple .test files with config, variables, requests, and assertions
Full Compiler Pipeline
Scanner, parser, type checker, and code generator with comprehensive error handling
JUnit 5 Generation
Each test block becomes a @Test method with HttpClient requests and assertions
Rich Assertions
Status codes, headers, and body content validation with contains/equals semantics
HTTP Methods Support
GET, POST, PUT, DELETE with custom headers and request bodies
Variable Interpolation
Define string or integer variables with let and reference them using $name syntax
Challenges
- Designing grammar rules that stay expressive but unambiguous.
- Ensuring semantic checks catch invalid types early before generation.
- Generating readable Java test output without sacrificing correctness.
Language Structure
Configuration Block
Optional global settings for base URL and default headers
config {
base_url = "http://localhost:8080";
header "Content-Type" = "application/json";
}Variable Declarations
Define reusable values with type safety
let userId = 123; let token = "Bearer abc123";
Test Blocks
Each test includes requests and assertions
test LoginTest {
POST "/api/login" {
body = "{\"username\":\"admin\"}";
};
expect status = 200;
expect body contains "token";
}Project Links
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