lashtest 0.2.1

A Python library for writing expressive, readable API tests

lashtest

A Python library for writing expressive, readable API tests with built-in Allure reporting.

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Features

• Fluent builder API — chain methods to build requests in one expression
• Rich assertions — assert status, JSON body, headers, cookies, response time, JSONPath, JSON Schema, and XML with XPath
• XML support — XPath queries with automatic namespace detection for SOAP, RSS, Atom, and SVG
• Multiple auth strategies — Bearer token, Basic auth, API key
• Retry with exponential backoff — configurable per-request
• File uploads — multipart form data with automatic handle cleanup
• Allure integration — requests and responses auto-attached as report steps
• Test decorators — @authenticated, @title, @severity, @description, @tag, @link
• Fake data generator — built-in fake for names, emails, phone numbers, addresses
• CLI runner — lashtest run collects and runs tests, lashtest report generates HTML reports
• SSL auto-detection — finds the system CA bundle on macOS, Linux, and Windows without configuration

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Installation

pip install lashtest

To also install development tools (coverage):

pip install "lashtest[dev]"

Requirements: Python 3.9+, and Allure CLI for HTML report generation.

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Quick start

from lashtest import APIClient

def test_get_user():
    with APIClient('https://jsonplaceholder.typicode.com').get('/users/1') as response:
        response.assert_status(200) \
                .assert_json_contains({'id': 1}) \
                .assert_response_time(2.0)

Run it:

lashtest run tests/

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Table of contents

• Client configuration
• Making requests
• Assertions
  • Status
  • JSON body
  • JSONPath
  • Headers and cookies
  • Performance
  • XML body
• Authentication
• Retry logic
• File uploads
• Test decorators
• Fake data
• Allure reporting
• CLI reference
• Error reference

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Client configuration

APIClient is the entry point. All configuration methods return self and can be chained.

from lashtest import APIClient
from lashtest.http import BearerToken

client = (
    APIClient('https://api.example.com')
    .with_base_path('/v1')
    .with_auth(BearerToken('my-token'))
    .with_header('X-Request-ID', 'test-suite')
    .with_timeout(10.0)
)

Method	Description
with_base_path(path)	Prefix applied to every endpoint (must start with /)
with_header(key, value)	Add a default header sent with every request
with_headers(headers)	Add multiple default headers at once
with_auth(auth)	Set default authentication (see Authentication)
with_timeout(seconds)	Default timeout in seconds (default: 30)
with_ssl_verification(verify)	True, False, or path to a CA bundle file
with_cookies(cookies)	Set session-level cookies
clear_cookies()	Remove all session cookies

Context manager

Use APIClient as a context manager to automatically close the underlying session:

with APIClient('https://api.example.com') as client:
    with client.get('/health') as response:
        response.assert_ok()

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Making requests

Call .get(), .post(), .put(), .patch(), or .delete() on the client to get a Request builder. Use it as a context manager — it executes the request and yields the Response.

# GET with query parameters
with client.get('/users').with_param('page', '2').with_param('limit', '10') as response:
    response.assert_ok()

# POST with JSON body
with client.post('/users').with_json({'name': 'Alice', 'email': '[e-mail]'}) as response:
    response.assert_status(201)

# PUT with JSON body
with client.put('/users/1').with_json({'name': 'Alice Updated'}) as response:
    response.assert_ok()

# PATCH
with client.patch('/users/1').with_json({'email': '[e-mail]'}) as response:
    response.assert_ok()

# DELETE
with client.delete('/users/1') as response:
    response.assert_status(204)

Request builder methods

All methods return self and can be chained before the with statement.

Method	Description
with_header(key, value)	Add a request-level header
with_param(key, value)	Add a query string parameter
with_params(params)	Add multiple query string parameters
with_json(body)	Set JSON body and Content-Type: application/json
with_body(body)	Set raw body
with_data(data)	Set form-encoded body
with_auth(auth)	Override the client-level auth for this request
with_timeout(seconds)	Override the client-level timeout for this request
with_file(field, path)	Attach a file for multipart upload (see File uploads)
with_retry(...)	Configure retry logic (see Retry logic)

Accessing the response

The context manager returns a Response object:

with client.get('/users/1') as response:
    print(response.status_code)   # int
    print(response.headers)       # dict
    print(response.text)          # str
    print(response.json())        # dict or list
    print(response.elapsed)       # float (seconds)
    print(response.ok)            # bool (True if 2xx)

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Assertions

All assertion methods return self, so they can be chained.

with client.get('/users/1') as response:
    response \
        .assert_status(200) \
        .assert_ok() \
        .assert_header('Content-Type') \
        .assert_json_path('$.name', 'Alice') \
        .assert_response_time(1.5)

Status

response.assert_status(200)   # exact status code
response.assert_ok()          # any 2xx status

JSON body

# Exact match
response.assert_json({'id': 1, 'name': 'Alice'})

# Subset match — only checks specified keys
response.assert_json_contains({'id': 1})

# JSON Schema validation
schema = {
    'type': 'object',
    'properties': {
        'id':   {'type': 'integer'},
        'name': {'type': 'string'},
    },
    'required': ['id', 'name'],
}
response.assert_json_schema(schema)

JSONPath

Uses JSONPath expressions via jsonpath_ng.

response.assert_json_path('$.id', 1)                    # value match
response.assert_json_path_type('$.id', int)             # type match
response.assert_json_path_exists('$.address.city')      # existence check

Headers and cookies

response.assert_header('Content-Type')                       # header exists
response.assert_header('Content-Type', 'application/json')  # header value match

response.assert_cookie_exists('session_id')
response.assert_cookie_value('theme', 'dark')

Performance

response.assert_response_time(0.5)   # must respond in under 0.5 seconds

XML body

Test APIs that return XML (SOAP, RSS, Atom, SVG, etc.) with XPath expressions and automatic namespace support.

# Basic XPath selection and text assertion
response.assertions.xml.xpath('//book[1]/title').text.eq('Python Guide')

# Count elements
response.assertions.xml.xpath('//book').count.gte(5)

# Assert element exists
response.assertions.xml.xpath('//user[@id="123"]').exists()

# Attribute assertions
response.assertions.xml.xpath('//book[@id="123"]').attribute('author').contains('Smith')

# Collection assertions on multiple nodes via .all()
response.assertions.xml.xpath('//book').all().text.contains('Python')

# First and nth node selection
response.assertions.xml.xpath('//item').first.text.eq('First Item')
response.assertions.xml.xpath('//item').nth(2).text.eq('Second Item')

Automatic Namespace Support

Namespaces are automatically detected — no configuration needed. Works with:

# SOAP envelope
response.assertions.xml.xpath('//soap:Body').exists()

# Atom feed
response.assertions.xml.xpath('//entry/title').text.eq('Latest Post')

# Default namespace
response.assertions.xml.xpath('//book').count.gte(1)

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Authentication

Import auth classes from lashtest.http:

from lashtest.http import BearerToken, BasicAuth, APIKey

Bearer token

client = APIClient('https://api.example.com').with_auth(BearerToken('eyJhbGci...'))

Adds Authorization: Bearer <token> to every request.

Basic auth

client = APIClient('https://api.example.com').with_auth(BasicAuth('username', 'password'))

Adds Authorization: Basic <base64(username:password)> to every request.

API key

# Default header name: X-API-KEY
client = APIClient('https://api.example.com').with_auth(APIKey(api_key='secret'))

# Custom header name
client = APIClient('https://api.example.com').with_auth(APIKey(header_name='X-Custom-Key', api_key='secret'))

Per-request override

# Client has no auth, but this one request uses a token
with client.get('/admin').with_auth(BearerToken('admin-token')) as response:
    response.assert_ok()

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Retry logic

Call .with_retry() on any request to enable automatic retries with exponential backoff.

with (
    client.post('/submit')
    .with_json({'data': 'value'})
    .with_retry(max_attempts=3, on_status=[500, 502, 503, 504])
) as response:
    response.assert_ok()

Parameter	Type	Default	Description
max_attempts	int	—	Maximum number of attempts (required)
on_status	list[int]	[500, 502, 503, 504]	Retry on these status codes
raise_on_exhausted	bool	False	Raise MaxRetriesExceededError after all attempts fail

Backoff schedule: 2^(attempt-1) seconds — 1 s, 2 s, 4 s, …

from lashtest import MaxRetriesExceededError

try:
    with client.get('/flaky').with_retry(max_attempts=3, raise_on_exhausted=True) as response:
        response.assert_ok()
except MaxRetriesExceededError as e:
    print(f"Failed after {e.retries} attempts, last status: {e.status_code}")

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File uploads

Use .with_file(field, path) for multipart file uploads. File handles are opened and closed automatically.

with client.post('/upload').with_file('document', '/path/to/report.pdf') as response:
    response.assert_status(201)

Multiple files:

with (
    client.post('/upload')
    .with_file('avatar', '/path/to/photo.jpg')
    .with_file('resume', '/path/to/cv.pdf')
) as response:
    response.assert_ok()

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Test decorators

Import decorators from lashtest.decorators:

from lashtest.decorators import authenticated, title, severity, description, tag, link

@authenticated

Injects authentication into every request made by self.client inside the decorated test. The original client is restored after each test, even if the test raises.

Method-level:

from lashtest.decorators import authenticated
from lashtest.http import BearerToken

class TestUsers:
    client = APIClient('https://api.example.com')

    @authenticated(BearerToken('my-token'))
    def test_get_profile(self):
        with self.client.get('/profile') as response:
            response.assert_ok()

Class-level — applies to all test_* methods automatically:

@authenticated(BasicAuth('admin', 'secret'))
class TestAdminEndpoints:
    client = APIClient('https://api.example.com')

    def test_list_users(self):
        with self.client.get('/admin/users') as response:
            response.assert_ok()

    def test_delete_user(self):
        with self.client.delete('/admin/users/1') as response:
            response.assert_status(204)

Allure decorators

These are thin wrappers around the corresponding allure decorators.

@title("User creation returns 201")
@severity('critical')
@description("Verifies that POST /users creates a new user and returns the created resource.")
@tag('smoke', 'users')
@link('https://jira.example.com/browse/API-42', name='API-42')
def test_create_user():
    ...

Decorator	Description
@title(text)	Sets the test title in the Allure report
@severity(level)	blocker, critical, normal, minor, trivial
@description(text)	Adds a description to the test in the report
@tag(*tags)	Marks tests for filtering with -t
@link(url, name)	Links to an external resource (JIRA, docs, etc.)

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Fake data

fake provides simple, dependency-free test data generation:

from lashtest.utils import fake

fake.name()                       # 'Alice Martin'
fake.email()                      # '[e-mail]'
fake.phone()                      # '[phone]'
fake.phone(country_code='+1')     # '[phone]'
fake.address()                    # '12 Rue de Rivoli, Paris, France'

Use it directly in test payloads:

def test_create_user():
    with client.post('/users').with_json({
        'name':    fake.name(),
        'email':   fake.email(),
        'phone':   fake.phone(),
        'address': fake.address(),
    }) as response:
        response.assert_status(201)

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Allure reporting

Every request and response is automatically recorded as an Allure step with the body attached as an artifact.

Viewing reports

Step 1 — Run tests and collect results:

lashtest run tests/ --allure-dir allure-results

Step 2 — Generate and open the HTML report:

lashtest report

Or using the Allure CLI directly:

allure serve allure-results

Enhancing reports

from lashtest.decorators import title, severity, description

@title("POST /users returns 201 with valid payload")
@severity('critical')
@description("Ensures the user creation endpoint validates input and returns the created resource.")
def test_create_user():
    with client.post('/users').with_json({'name': fake.name(), 'email': fake.email()}) as response:
        response.assert_status(201).assert_json_path_exists('$.id')

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CLI reference

lashtest run

Discover and run API tests.

Usage: lashtest run [PATH] [OPTIONS]

Arguments:
  PATH  Test directory or file  [default: tests/]

Options:
  -v, --verbose              Enable verbose output
  -r, --allure-dir TEXT      Directory for Allure results  [default: allure-results]
  -t, --tags TEXT            Filter tests by tag (comma-separated)
  --help                     Show this message and exit.

Examples:

# Run all tests
lashtest run

# Run a specific file
lashtest run tests/test_users.py

# Filter by tag
lashtest run -t smoke

# Custom results directory with verbose output
lashtest run -r ci-results -v

lashtest report

Generate an HTML Allure report from collected results.

Usage: lashtest report [RESULTS-DIR] [OUTPUT-DIR]

Arguments:
  RESULTS-DIR  Allure results directory  [default: allure-results]
  OUTPUT-DIR   Output HTML report directory  [default: allure-report]

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Error reference

All exceptions inherit from lashtest.APIError.

Exception	When raised
APIError	Base class — catch this to handle any library error
HTTPError	The server returned an HTTP error response
APITimeoutError	The request exceeded the configured timeout
APIConnectionError	Could not connect to the server
InvalidURL	The URL or endpoint is malformed
JSONDecodeError	The response body is not valid JSON
AuthenticationError	Authentication failed
MaxRetriesExceededError	All retry attempts failed (only when raise_on_exhausted=True)

from lashtest import APIClient, APIError, APITimeoutError, MaxRetriesExceededError

try:
    with APIClient('https://api.example.com').with_timeout(5.0).get('/slow') as response:
        response.assert_ok()
except APITimeoutError as e:
    print(f"Timed out after {e.timeout}s")
except APIError as e:
    print(f"Request failed: {e}")

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Project structure

Recommended layout for a test project using lashtest:

my-api-tests/
├── pyproject.toml
├── conftest.py          # shared fixtures
└── tests/
    ├── test_users.py
    ├── test_products.py
    └── test_auth.py

conftest.py:

import pytest
from lashtest import APIClient
from lashtest.http import BearerToken

@pytest.fixture(scope='session')
def client():
    return (
        APIClient('https://api.example.com')
        .with_base_path('/v1')
        .with_auth(BearerToken('token'))
        .with_timeout(10.0)
    )

tests/test_users.py:

from lashtest.decorators import title, severity, tag
from lashtest.utils import fake

@tag('users', 'smoke')
class TestUsers:

    @title("GET /users returns a list")
    @severity('normal')
    def test_list_users(self, client):
        with client.get('/users') as response:
            response.assert_ok() \
                    .assert_json_path_exists('$[0].id')

    @title("POST /users creates a user")
    @severity('critical')
    def test_create_user(self, client):
        with client.post('/users').with_json({
            'name':  fake.name(),
            'email': fake.email(),
        }) as response:
            response.assert_status(201) \
                    .assert_json_path_exists('$.id')

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Contributing

See CONTRIBUTING.md.

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License

MIT — see LICENCE.