Mocking

Available since v0.6.4

When writing tests for function which use the Prisma client, it can be difficult to have a real database running to test with. To combat this, you can enable the mocking feature on prisma-client-rust and prisma-client-rust-cli and create a 'mock' client that runs queries using data you provide beforehand. This allows you to define the expected result of a query and then perform tests using those expected results.

The examples use the following Prisma schema:

model Post {
    id    String   @default(cuid()) @id
    title String
}

Say you have a function get_post_title:

use prisma::{PrismaClient, post};
use prisma_client_rust::queries;
 
async fn get_post_title(
    client: &PrismaClient,
    post_id: String,
) -> queries::Result<Option<String>> {
    let post = client.post().find_unique(post::id::equals(post_id)).await?;
 
    post.map(|post| post.title)
}

To write a unit test, first create a mock client and mock store with PrismaClient::_mock, define your expectations via the mock store, and run the test. The mock client will use data from the mock store to resolve queries.

#[cfg(test)]
mod test {
	use super::*;
 
	#[tokio::test]
	async fn gets_title() -> queries::Result<()> {
		let (client, mock) = PrismaClient::_mock().await;
 
		let id = "123".to_string();
		let expected_title = "Test".to_string();
 
		mock.expect(
			// First argument is query without calling 'exec'
			client.post().find_unique(post::id::equals(post_id)),
			// Second argument is expected return type.
			// This will fail to compile if it does not match
			// the return type of the query
			post::Data {
				id: id.clone(),
				title: expected_title.to_string(),
			},
		)
		.await;
 
		 let title = get_post_title(&client, id).await?;
 
		 assert_eq!(title, Some(expected_title));
	}
}

Partial Types Error Handling