How to Run Concurrent Tests Across Multiple Packages in Go Without Database Contention?

Go: Addressing Test Concurrency Across Multiple Packages

Running tests for multiple packages under a subdirectory using go test can be challenging when tests rely on global variables and local database servers. While go test ./... runs the tests, it fails due to potential contention in the database.

Understanding the Issue

The issue arises because go test ./... executes tests for different packages in parallel. When each test file contains global variables with database pointers and the tests rely on database operations, this parallelism can lead to test failures caused by data contention.

Potential Fixes

1. Running Tests Serially

To force sequential testing across packages, consider using the undocumented flag -p 1 when running go test. This flag forces all packages to build and test sequentially.

<code class="bash">go test -p 1 ./...</code>

2. Using a Shell Script

If -p 1 is not suitable, consider using a shell script that emulates go test ./... behavior but forces sequential testing. This can be achieved by listing subdirectories with *.go files, removing duplicates, and executing go test on each subdirectory one by one.

<code class="bash">find . -name '*.go' -printf '%h\n' | sort -u | xargs -n1 -P1 go test</code>

3. Database-Aware Testing

Another approach is to modify the test code to be more concurrency-aware. This can involve using package-level databases and deferring database initialization and teardown to the beginning and end of each test, respectively. It's crucial to ensure that database operations are synchronous and that each test has its own set of database resources.

Example:

Below is an example of how to ensure database isolation in each test:

<code class="go">import (
    "database/sql"
    "testing"
)

type DBWrapper struct {
    *sql.DB
}

func (db DBWrapper) TearDown(t *testing.T) {
    if err := db.Close(); err != nil {
        t.Errorf("Failed to close database: %v", err)
    }
}

func TestDatabase(t *testing.T) {
    defer DBWrapper{sql.Open(...)}.TearDown(t)

    // Conduct test operations using the isolated DBWrapper
}</code>

By using these techniques, it's possible to run tests for multiple packages that involve database operations without encountering contention-related failures.

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