How to Unit Test SQL in MySQL

How can I perform unit testing on MySQL stored procedures?

Unit testing in MySQL validates stored procedures, functions, and queries by comparing actual results with expected values in isolated, repeatable tests.

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Description

Why unit test MySQL stored code?

Unit tests uncover logic defects in SQL long before they reach dashboards or applications, saving rework and protecting data quality.

What pattern does a SQL unit test follow?

Every test uses the Arrange-Act-Assert pattern: insert controlled data, call the routine under test, then compare the result with an expected value.

How do I isolate tests safely?

Wrap each test in a transaction and roll it back, or run tests in a dedicated schema created and dropped by the test runner.

How to create a tiny assertion helper?

The assert_equals() procedure raises an error when expected and actual values differ, causing the test to fail and the runner to stop.

assert_equals implementation

DELIMITER // CREATE PROCEDURE test.assert_equals( IN expected VARCHAR(255), IN actual VARCHAR(255), IN msg VARCHAR(255) ) BEGIN IF expected != actual THEN SIGNAL SQLSTATE '45000' SET MESSAGE_TEXT = CONCAT('Assertion failed: ', msg), MYSQL_ERRNO = 1644; END IF; END // DELIMITER ;

How do I write my first test?

The example below validates a get_customer_lifetime_value() function using ecommerce tables.Insert sample customers and orders, call the function, and assert the result.

Can I automate tests with external tools?

Yes. Run mysql with --batch, use the mysqltest utility, or integrate with pytest/JUnit by invoking scripts inside CI pipelines.

Best practices for MySQL unit tests

Keep fixtures small, reset state between tests, name tests descriptively, and fail fast with clear error messages.

Why How to Unit Test SQL in MySQL is important

How to Unit Test SQL in MySQL Example Usage


-- Test get_customer_lifetime_value() returns correct sum
START TRANSACTION;

-- Arrange
INSERT INTO Customers(id,name,email,created_at)
VALUES (10,'Grace Hopper','grace@example.com',NOW());
INSERT INTO Orders(id,customer_id,order_date,total_amount)
VALUES (101,10,NOW(),80.00),
       (102,10,NOW(),20.00);

-- Act
SET @value := get_customer_lifetime_value(10);

-- Assert
CALL test.assert_equals(100.00,@value,'Grace Hopper lifetime value');

ROLLBACK;

How to Unit Test SQL in MySQL Syntax


-- Create a test schema
CREATE SCHEMA test;
USE test;

-- Helper assertion procedure
DELIMITER //
CREATE PROCEDURE assert_equals(
    IN expected DECIMAL(10,2),
    IN actual   DECIMAL(10,2),
    IN msg      VARCHAR(255)
)
BEGIN
    IF expected != actual THEN
        SIGNAL SQLSTATE '45000'
            SET MESSAGE_TEXT = CONCAT('Assertion failed: ', msg),
                MYSQL_ERRNO = 1644;
    END IF;
END //
DELIMITER ;

-- Template for a unit test
START TRANSACTION;
/* Arrange */
INSERT INTO Customers(id,name,email,created_at) VALUES(1,'Ada','ada@example.com',NOW());
INSERT INTO Orders(id,customer_id,order_date,total_amount) VALUES(1,1,NOW(),120.00);

/* Act */
SET @lv := get_customer_lifetime_value(1);

/* Assert */
CALL assert_equals(120.00,@lv,'Lifetime value should equal order total');

ROLLBACK;

Common Mistakes

Running tests on production data—this pollutes critical tables and makes results non-deterministic. Fix by isolating tests in a disposable schema or a transaction you roll back.
Skipping assertions—merely running a procedure is not a test. Always compare the actual result to an expected value with an assertion helper so failures surface immediately.