Example approaches for unit and integration testing with an AWS SDK - Amazon Simple Storage Service

Example approaches for unit and integration testing with an AWS SDK

The following code example shows how to examples for best-practice techniques when writing unit and integration tests using an AWS SDK.

Rust
SDK for Rust
Note

There's more on GitHub. Find the complete example and learn how to set up and run in the AWS Code Examples Repository.

Cargo.toml for testing examples.

[package]
name = "testing-examples"
version = "0.1.0"
authors = [
  "John Disanti <jdisanti@amazon.com>",
  "Doug Schwartz <dougsch@amazon.com>",
]
edition = "2021"

[dependencies]
async-trait = "0.1.51"
aws-config = { version = "1.0.1", features = ["behavior-version-latest"] }
aws-credential-types = { version = "1.0.1", features = [ "hardcoded-credentials", ] }
aws-sdk-s3 = { version = "1.4.0" }
aws-smithy-types = { version = "1.0.1" }
aws-smithy-runtime = { version = "1.0.1", features = ["test-util"] }
aws-smithy-runtime-api = { version = "1.0.1", features = ["test-util"] }
aws-types = { version = "1.0.1" }
clap = { version = "~4.4", features = ["derive"] }
http = "0.2.9"
mockall = "0.11.4"
serde_json = "1"
tokio = { version = "1.20.1", features = ["full"] }
tracing-subscriber = { version = "0.3.15", features = ["env-filter"] }

[[bin]]
name = "main"
path = "src/main.rs"

Unit testing example using automock and a service wrapper.


use aws_sdk_s3 as s3;
#[allow(unused_imports)]
use mockall::automock;

use s3::operation::list_objects_v2::{ListObjectsV2Error, ListObjectsV2Output};

#[cfg(test)]
pub use MockS3Impl as S3;
#[cfg(not(test))]
pub use S3Impl as S3;

#[allow(dead_code)]
pub struct S3Impl {
    inner: s3::Client,
}

#[cfg_attr(test, automock)]
impl S3Impl {
    #[allow(dead_code)]
    pub fn new(inner: s3::Client) -> Self {
        Self { inner }
    }

    #[allow(dead_code)]
    pub async fn list_objects(
        &self,
        bucket: &str,
        prefix: &str,
        continuation_token: Option<String>,
    ) -> Result<ListObjectsV2Output, s3::error::SdkError<ListObjectsV2Error>> {
        self.inner
            .list_objects_v2()
            .bucket(bucket)
            .prefix(prefix)
            .set_continuation_token(continuation_token)
            .send()
            .await
    }
}

#[allow(dead_code)]
pub async fn determine_prefix_file_size(
    // Now we take a reference to our trait object instead of the S3 client
    // s3_list: ListObjectsService,
    s3_list: S3,
    bucket: &str,
    prefix: &str,
) -> Result<usize, s3::Error> {
    let mut next_token: Option<String> = None;
    let mut total_size_bytes = 0;
    loop {
        let result = s3_list
            .list_objects(bucket, prefix, next_token.take())
            .await?;

        // Add up the file sizes we got back
        for object in result.contents() {
            total_size_bytes += object.size().unwrap_or(0) as usize;
        }

        // Handle pagination, and break the loop if there are no more pages
        next_token = result.next_continuation_token.clone();
        if next_token.is_none() {
            break;
        }
    }
    Ok(total_size_bytes)
}

#[cfg(test)]
mod test {
    use super::*;
    use mockall::predicate::eq;

    #[tokio::test]
    async fn test_single_page() {
        let mut mock = MockS3Impl::default();
        mock.expect_list_objects()
            .with(eq("test-bucket"), eq("test-prefix"), eq(None))
            .return_once(|_, _, _| {
                Ok(ListObjectsV2Output::builder()
                    .set_contents(Some(vec![
                        // Mock content for ListObjectsV2 response
                        s3::types::Object::builder().size(5).build(),
                        s3::types::Object::builder().size(2).build(),
                    ]))
                    .build())
            });

        // Run the code we want to test with it
        let size = determine_prefix_file_size(mock, "test-bucket", "test-prefix")
            .await
            .unwrap();

        // Verify we got the correct total size back
        assert_eq!(7, size);
    }

    #[tokio::test]
    async fn test_multiple_pages() {
        // Create the Mock instance with two pages of objects now
        let mut mock = MockS3Impl::default();
        mock.expect_list_objects()
            .with(eq("test-bucket"), eq("test-prefix"), eq(None))
            .return_once(|_, _, _| {
                Ok(ListObjectsV2Output::builder()
                    .set_contents(Some(vec![
                        // Mock content for ListObjectsV2 response
                        s3::types::Object::builder().size(5).build(),
                        s3::types::Object::builder().size(2).build(),
                    ]))
                    .set_next_continuation_token(Some("next".to_string()))
                    .build())
            });
        mock.expect_list_objects()
            .with(
                eq("test-bucket"),
                eq("test-prefix"),
                eq(Some("next".to_string())),
            )
            .return_once(|_, _, _| {
                Ok(ListObjectsV2Output::builder()
                    .set_contents(Some(vec![
                        // Mock content for ListObjectsV2 response
                        s3::types::Object::builder().size(3).build(),
                        s3::types::Object::builder().size(9).build(),
                    ]))
                    .build())
            });

        // Run the code we want to test with it
        let size = determine_prefix_file_size(mock, "test-bucket", "test-prefix")
            .await
            .unwrap();

        assert_eq!(19, size);
    }
}

Integration testing example using StaticReplayClient.


use aws_sdk_s3 as s3;

#[allow(dead_code)]
pub async fn determine_prefix_file_size(
    // Now we take a reference to our trait object instead of the S3 client
    // s3_list: ListObjectsService,
    s3: s3::Client,
    bucket: &str,
    prefix: &str,
) -> Result<usize, s3::Error> {
    let mut next_token: Option<String> = None;
    let mut total_size_bytes = 0;
    loop {
        let result = s3
            .list_objects_v2()
            .prefix(prefix)
            .bucket(bucket)
            .set_continuation_token(next_token.take())
            .send()
            .await?;

        // Add up the file sizes we got back
        for object in result.contents() {
            total_size_bytes += object.size().unwrap_or(0) as usize;
        }

        // Handle pagination, and break the loop if there are no more pages
        next_token = result.next_continuation_token.clone();
        if next_token.is_none() {
            break;
        }
    }
    Ok(total_size_bytes)
}

#[allow(dead_code)]
fn make_s3_test_credentials() -> s3::config::Credentials {
    s3::config::Credentials::new(
        "ATESTCLIENT",
        "astestsecretkey",
        Some("atestsessiontoken".to_string()),
        None,
        "",
    )
}

#[cfg(test)]
mod test {
    use super::*;
    use aws_config::BehaviorVersion;
    use aws_sdk_s3 as s3;
    use aws_smithy_runtime::client::http::test_util::{ReplayEvent, StaticReplayClient};
    use aws_smithy_types::body::SdkBody;

    #[tokio::test]
    async fn test_single_page() {
        let page_1 = ReplayEvent::new(
                http::Request::builder()
                    .method("GET")
                    .uri("https://test-bucket.s3.us-east-1.amazonaws.com/?list-type=2&prefix=test-prefix")
                    .body(SdkBody::empty())
                    .unwrap(),
                http::Response::builder()
                    .status(200)
                    .body(SdkBody::from(include_str!("./testing/response_1.xml")))
                    .unwrap(),
            );
        let replay_client = StaticReplayClient::new(vec![page_1]);
        let client: s3::Client = s3::Client::from_conf(
            s3::Config::builder()
                .behavior_version(BehaviorVersion::latest())
                .credentials_provider(make_s3_test_credentials())
                .region(s3::config::Region::new("us-east-1"))
                .http_client(replay_client.clone())
                .build(),
        );

        // Run the code we want to test with it
        let size = determine_prefix_file_size(client, "test-bucket", "test-prefix")
            .await
            .unwrap();

        // Verify we got the correct total size back
        assert_eq!(7, size);
        replay_client.assert_requests_match(&[]);
    }

    #[tokio::test]
    async fn test_multiple_pages() {
        let page_1 = ReplayEvent::new(
                http::Request::builder()
                    .method("GET")
                    .uri("https://test-bucket.s3.us-east-1.amazonaws.com/?list-type=2&prefix=test-prefix")
                    .body(SdkBody::empty())
                    .unwrap(),
                http::Response::builder()
                    .status(200)
                    .body(SdkBody::from(include_str!("./testing/response_multi_1.xml")))
                    .unwrap(),
            );
        let page_2 = ReplayEvent::new(
                http::Request::builder()
                    .method("GET")
                    .uri("https://test-bucket.s3.us-east-1.amazonaws.com/?list-type=2&prefix=test-prefix&continuation-token=next")
                    .body(SdkBody::empty())
                    .unwrap(),
                http::Response::builder()
                    .status(200)
                    .body(SdkBody::from(include_str!("./testing/response_multi_2.xml")))
                    .unwrap(),
            );
        let replay_client = StaticReplayClient::new(vec![page_1, page_2]);
        let client: s3::Client = s3::Client::from_conf(
            s3::Config::builder()
                .behavior_version(BehaviorVersion::latest())
                .credentials_provider(make_s3_test_credentials())
                .region(s3::config::Region::new("us-east-1"))
                .http_client(replay_client.clone())
                .build(),
        );

        // Run the code we want to test with it
        let size = determine_prefix_file_size(client, "test-bucket", "test-prefix")
            .await
            .unwrap();

        assert_eq!(19, size);

        replay_client.assert_requests_match(&[]);
    }
}

For a complete list of AWS SDK developer guides and code examples, see Developing with Amazon S3 using the AWS SDKs. This topic also includes information about getting started and details about previous SDK versions.