Table-Driven Test Generator

Purpose: Generate a complete, runnable test file for any function using table-driven tests (it.each / test.each in Vitest/Jest, parametrize in pytest). Covers: happy path, boundary values, null/undefined inputs, empty collections, async rejection, and type coercion edge cases. Output can be pasted directly into a .test.ts or _test.py file and run immediately.

Invocation

/test <function-signature-and-implementation>

Examples:

• /test function add(a: number, b: number): number { return a + b }
• /test async function fetchUser(id: string): Promise<User | null>
• /test def calculate_discount(price: float, pct: float) -> float:

Process

Step 1: Analyze the Function

Identify:

• Inputs: types, constraints, optional vs required
• Output: return type, possible return values
• Side effects: async operations, mutations, I/O
• Failure modes: throws, returns null, rejects, etc.

Step 2: Design Test Cases

For every function, generate tests covering:

Step 3: Write the Test File

Vitest / Jest output:

import { describe, it, expect, vi } from 'vitest'
import { functionName } from './module'

describe('functionName', () => {
  it.each([
    // [description, input1, input2, ..., expected]
    ['happy path: typical inputs', arg1, arg2, expectedOutput],
    ['boundary: zero value', 0, arg2, expectedForZero],
    ['boundary: negative', -1, arg2, expectedForNegative],
    ['null input: first arg null', null, arg2, expectedForNull],
  ])('%s', (description, input1, input2, expected) => {
    // Arrange
    const input = buildInput(input1, input2)

    // Act
    const result = functionName(input1, input2)

    // Assert
    expect(result).toEqual(expected)
  })

  it('throws on invalid input', () => {
    // Arrange + Act + Assert
    expect(() => functionName(invalidInput)).toThrow('Expected error message')
  })

  it('handles async rejection gracefully', async () => {
    // Arrange
    vi.mocked(dependency).mockRejectedValue(new Error('Network error'))

    // Act + Assert
    await expect(functionName(input)).rejects.toThrow('Network error')
  })
})

pytest output:

import pytest
from module import function_name

@pytest.mark.parametrize("description,input_val,expected", [
    ("happy path: typical input", typical_input, expected_output),
    ("boundary: zero", 0, expected_for_zero),
    ("boundary: negative", -1, expected_for_neg),
    ("None input", None, expected_for_none),
])
def test_function_name(description, input_val, expected):
    # Arrange + Act
    result = function_name(input_val)

    # Assert
    assert result == expected, f"Failed: {description}"

def test_function_name_raises_on_invalid():
    with pytest.raises(ValueError, match="Expected message"):
        function_name(invalid_input)

Rules

• Every test must follow AAA (Arrange / Act / Assert) with comment labels
• The table must have at least 5 rows: 1 happy path + 4 edge cases
• Async functions must include at least one rejection test
• No placeholder text in the output — all test values must be concrete
• If the function has side effects (DB write, HTTP call): add a mock setup block
• Output must be runnable as-is — the only acceptable TODO is "fill in real mock return value"
• Detect framework from function syntax: TypeScript → Vitest, Python → pytest, Go → testing.T table tests

Playground

<span style='color:#8b949e'> if v < min { return min }</span> <span style='color:#8b949e'> if v > max { return max }</span> <span style='color:#8b949e'> return v</span> <span style='color:#8b949e'>}</span></pre></div><div class='panel'><div class='label'>Output: Table-driven tests</div><pre><span style='color:#58a6ff'>func TestClamp(t *testing.T) {</span> <span style='color:#8b949e'> tests := []struct{</span> <span style='color:#8b949e'> name string</span> <span style='color:#8b949e'> v,mn,mx int</span> <span style='color:#8b949e'> want int</span> <span style='color:#8b949e'> }{</span> <span style='color:#8b949e'> {"below min", -5, 0, 10, 0},</span> <span style='color:#8b949e'> {"above max", 15, 0, 10, 10},</span> <span style='color:#8b949e'> {"in range", 5, 0, 10, 5},</span> <span style='color:#8b949e'> {"at min", 0, 0, 10, 0},</span> <span style='color:#8b949e'> {"at max", 10, 0, 10, 10},</span> <span style='color:#8b949e'> }</span>

<span style='color:#8b949e'> for _, tc := range tests {</span> <span style='color:#8b949e'> t.Run(tc.name, func(t *testing.T) {</span> <span style='color:#8b949e'> got := Clamp(tc.v, tc.mn, tc.mx)</span> <span style='color:#8b949e'> if got != tc.want {</span> <span style='color:#8b949e'> t.Errorf("got %d want %d",</span> <span style='color:#8b949e'> got, tc.want)</span> <span style='color:#8b949e'> }</span> <span style='color:#8b949e'> })</span> <span style='color:#8b949e'> }</span> <span style='color:#8b949e'>}</span></pre></div></div></body></html>