assertion-synthesizer

Generate test assertions from existing code implementation. Use when the user has implementation code without tests or incomplete test coverage, and needs assertions synthesized by analyzing the code's behavior, inputs, outputs, and state changes. Supports Python (pytest/unittest), Java (JUnit/AssertJ), and JavaScript/TypeScript (Jest/Chai). Handles equality checks, collections, exceptions, and state verification.

Install with Tessl CLI

npx tessl i github:ArabelaTso/Skills-4-SE --skill assertion-synthesizer

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Review — 82%

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Validation — 11 / 11 Passed

Validation for skill structure

SKILL.md

Review

Evals

Evaluation results

98%

20%

Library Catalog: Write Test Suite

Python pytest assertion patterns

Criteria

Without context

With context

Arrange-Act-Assert structure

75%

Descriptive test names

100%

pytest.raises with match parameter

100%

Initial state assertion

100%

Post-operation state assertion

100%

Parametrize decorator used

100%

Boundary and empty cases

100%

All error paths covered

100%

Collection length assertion

42%

100%

Collection membership assertion

100%

Specific equality assertions

100%

Exception message asserted

100%

Without context: $0.6534 · 5m 40s · 31 turns · 39 in / 8,433 out tokens

With context: $0.6989 · 4m 52s · 27 turns · 285 in / 8,473 out tokens

99%

Event Scheduler: Write Jest Test Suite

JavaScript/TypeScript Jest assertion patterns

Criteria

Without context

With context

toBe or toEqual for value equality

100%

toContain for membership

100%

toHaveLength for array length

100%

toThrow with message string

100%

describe blocks for grouping

100%

Single behavior per test

85%

All throw paths tested

100%

Sorted/ordered result asserted

100%

Empty state tested

100%

Post-mutation state tested

100%

Boolean result tested

100%

Multiple tag sources in getAllTags

100%

Without context: $0.4791 · 5m 15s · 24 turns · 30 in / 7,795 out tokens

With context: $0.5409 · 4m 36s · 21 turns · 183 in / 7,674 out tokens

79%

-3%

Shopping Cart: Write JUnit Test Suite

Java JUnit AssertJ assertion patterns

Criteria

Without context

With context

assertThat fluent equality

100%

assertThat list contains

100%

assertThat list size

assertThatThrownBy with isInstanceOf

100%

hasMessage chained on assertThatThrownBy

100%

assertThat boolean matchers

100%

Explanatory phase comments

62%

25%

All exception paths covered

100%

Empty cart state tested

100%

List membership and size both asserted

Multiple exception classes tested

100%

Numeric calculation asserted

100%

Without context: $0.2947 · 2m 29s · 12 turns · 14 in / 5,711 out tokens

With context: $0.4207 · 2m 24s · 15 turns · 268 in / 6,370 out tokens

Evaluated: about 11 hours ago
Agent: Claude Code

Table of Contents

Library Catalog: Write Test Suite Event Scheduler: Write Jest Test Suite Shopping Cart: Write JUnit Test Suite

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