A snapshot is a saved state or image of a system, database, or file at a particular point in time.
In software development and testing, a snapshot is used to capture the exact state of an application or component at a specific moment. This can be useful for comparing changes over time or ensuring that the output of a function or the state of a component remains consistent.
For example, when testing a user interface component, a snapshot can save the rendered output. Future tests can then compare the current output with the saved snapshot to ensure that no unintended changes have occurred.
Simple Code Example (JavaScript using Jest):
import renderer from 'react-test-renderer';
import MyComponent from './MyComponent';
test('MyComponent renders correctly', () => {
const tree = renderer.create(<MyComponent />).toJSON();
expect(tree).toMatchSnapshot();
});
In this example, renderer.create
renders the MyComponent
and saves its output as a JSON object. The toMatchSnapshot
function then compares this output to a previously saved snapshot. If the output has changed, the test will fail, indicating that the component’s output is different from what was expected.