Test Schema

Test Schema

Write Vitest tests for Zod schemas in this backend template.

Quick Reference

Location: tests/schemas/{entity-name}.schema.test.ts Run tests: pnpm test -- tests/schemas/{entity-name}.schema.test.ts Watch mode: pnpm test:watch

Instructions

Step 1: Create the Test File

Create tests/schemas/{entity-name}.schema.test.ts mirroring the source structure.

Step 2: Import Dependencies

import { describe, it, expect } from "vitest";
import {
  {entity}Schema,
  create{Entity}Schema,
  update{Entity}Schema,
  {entity}QueryParamsSchema,
} from "@/schemas/{entity-name}.schema";

Step 3: Test Each Schema

Create a describe block for each schema with focused test cases.

Test Patterns

Base Entity Schema Tests

describe("{entity}Schema", () => {
  it("accepts valid {entity}", () => {
    const valid = {
      id: "1",
      // ... all required fields with valid values
      createdBy: "user-1",
      createdAt: new Date(),
      updatedAt: new Date(),
    };
    expect({entity}Schema.parse(valid)).toEqual(valid);
  });

  it("rejects missing required fields", () => {
    expect(() => {entity}Schema.parse({})).toThrow();
  });

  it("rejects invalid field types", () => {
    expect(() =>
      {entity}Schema.parse({
        id: 123, // should be string
        // ... other fields
      })
    ).toThrow();
  });

  it("accepts optional timestamps as undefined", () => {
    const valid = {
      id: "1",
      // ... required fields only, no timestamps
      createdBy: "user-1",
    };
    expect({entity}Schema.parse(valid)).toMatchObject({ id: "1" });
  });
});

Create DTO Schema Tests

describe("create{Entity}Schema", () => {
  it("accepts valid create data", () => {
    const valid = {
      // Only fields that user provides (no id, createdBy, timestamps)
      fieldName: "value",
    };
    expect(create{Entity}Schema.parse(valid)).toEqual(valid);
  });

  it("rejects empty required fields", () => {
    expect(() => create{Entity}Schema.parse({ fieldName: "" })).toThrow();
  });

  it("rejects missing required fields", () => {
    expect(() => create{Entity}Schema.parse({})).toThrow();
  });

  it("strips unknown fields", () => {
    const input = { fieldName: "value", unknownField: "ignored" };
    const parsed = create{Entity}Schema.parse(input);
    expect(parsed).not.toHaveProperty("unknownField");
  });
});

Update DTO Schema Tests

describe("update{Entity}Schema", () => {
  it("accepts partial update", () => {
    expect(update{Entity}Schema.parse({ fieldName: "updated" })).toEqual({
      fieldName: "updated",
    });
  });

  it("accepts empty object (no fields to update)", () => {
    expect(update{Entity}Schema.parse({})).toEqual({});
  });

  it("accepts multiple fields", () => {
    const update = { field1: "new1", field2: "new2" };
    expect(update{Entity}Schema.parse(update)).toEqual(update);
  });
});

Query Parameters Schema Tests

describe("{entity}QueryParamsSchema", () => {
  it("accepts empty object (all optional)", () => {
    expect({entity}QueryParamsSchema.parse({})).toEqual({});
  });

  it("coerces page and limit to numbers", () => {
    const parsed = {entity}QueryParamsSchema.parse({ page: "2", limit: "5" });
    expect(parsed.page).toBe(2);
    expect(parsed.limit).toBe(5);
  });

  it("accepts valid sortOrder values", () => {
    expect({entity}QueryParamsSchema.parse({ sortOrder: "asc" }).sortOrder).toBe("asc");
    expect({entity}QueryParamsSchema.parse({ sortOrder: "desc" }).sortOrder).toBe("desc");
  });

  it("rejects invalid sortOrder", () => {
    expect(() => {entity}QueryParamsSchema.parse({ sortOrder: "invalid" })).toThrow();
  });

  it("accepts entity-specific filters", () => {
    // Test any custom filters added to the query params
    expect({entity}QueryParamsSchema.parse({ createdBy: "user-1" }).createdBy).toBe("user-1");
  });
});

ID Schema Tests (if separate)

describe("{entity}IdSchema", () => {
  it("accepts valid string ID", () => {
    expect({entity}IdSchema.parse("abc-123")).toBe("abc-123");
  });

  it("rejects non-string ID", () => {
    expect(() => {entity}IdSchema.parse(123)).toThrow();
  });
});

Testing Guidelines

What to Test

1. Happy path - Valid data passes validation
2. Missing required fields - Schema rejects incomplete data
3. Invalid types - Wrong data types are rejected
4. Empty strings - Required strings with .min(1) reject empty
5. Enum values - Only valid enum values accepted
6. Coercion - Query params coerce strings to numbers
7. Optional fields - Can be omitted without error
8. Default values - Defaults are applied correctly

Test Naming Conventions

Use descriptive it statements:

• "accepts valid {entity}" - Happy path
• "rejects missing required fields" - Validation failure
• "rejects invalid {field}" - Specific field validation
• "coerces {field} to {type}" - Type coercion
• "accepts optional {field} as undefined" - Optional handling
• "applies default value for {field}" - Default behavior

Import Rules

• Always use path aliases: import { x } from "@/schemas/..."
• Import from vitest: describe, it, expect
• Import z from zod only if testing generic schemas

Complete Example

See tests/schemas/note.schema.test.ts:

import { describe, it, expect } from "vitest";
import {
  noteSchema,
  createNoteSchema,
  updateNoteSchema,
  noteQueryParamsSchema,
} from "@/schemas/note.schema";

describe("noteSchema", () => {
  it("accepts valid note", () => {
    const valid = {
      id: "1",
      content: "Hello",
      createdBy: "user-1",
      createdAt: new Date(),
      updatedAt: new Date(),
    };
    expect(noteSchema.parse(valid)).toEqual(valid);
  });

  it("rejects missing required fields", () => {
    expect(() => noteSchema.parse({})).toThrow();
  });
});

describe("createNoteSchema", () => {
  it("accepts valid create note", () => {
    expect(createNoteSchema.parse({ content: "Hi" })).toEqual({
      content: "Hi",
    });
  });

  it("rejects empty content", () => {
    expect(() => createNoteSchema.parse({ content: "" })).toThrow();
  });

  it("rejects missing content", () => {
    expect(() => createNoteSchema.parse({})).toThrow();
  });
});

describe("updateNoteSchema", () => {
  it("accepts partial update", () => {
    expect(updateNoteSchema.parse({ content: "Updated" })).toEqual({
      content: "Updated",
    });
  });

  it("accepts empty object (no update)", () => {
    expect(updateNoteSchema.parse({})).toEqual({});
  });
});

describe("noteQueryParamsSchema", () => {
  it("coerces page and limit to numbers", () => {
    const parsed = noteQueryParamsSchema.parse({ page: "2", limit: "5" });
    expect(parsed.page).toBe(2);
    expect(parsed.limit).toBe(5);
  });

  it("accepts optional createdBy", () => {
    expect(noteQueryParamsSchema.parse({ createdBy: "user-1" }).createdBy).toBe(
      "user-1",
    );
  });

  it("accepts empty object (all optional)", () => {
    expect(noteQueryParamsSchema.parse({})).toEqual({});
  });
});

What NOT to Do

• Do NOT test implementation details - test behavior
• Do NOT use snapshots for simple schema validation
• Do NOT mock Zod - test actual schema parsing
• Do NOT skip edge cases - empty strings, wrong types, missing fields
• Do NOT forget to test coercion for query parameters