Why Do Tests Fail When Running Across Multiple Packages in Go Despite Using `-parallel 1`?

Concurrency Issues Arise When Running Tests Across Multiple Packages in Go

When working with multiple packages stored under a subdirectory within the src/ directory, executing tests for each package individually using go test is typically successful. However, when attempting to run all tests collectively using go test ./..., issues arise.

The tests execute, but ultimately fail when operating against local database servers due to contention between tests. Despite setting -parallel 1 to prevent database contention, the tests still fail. This suggests a problem with test sequencing.

Each test file contains two global variables:

<code class="go">var session *mgo.Session
var db *mgo.Database</code>

Additionally, it employs the following setup and teardown functions:

<code class="go">func setUp() {
   s, err := cfg.GetDBSession()
   if err != nil {
       panic(err)
   }

   session = s

   db = cfg.GetDB(session)

   db.DropDatabase()
}

func tearDown() {
   db.DropDatabase()

   session.Close()
}</code>

Each test begins with setUp() and ends with tearDown(). cfg is defined as follows:

<code class="go">package cfg

import (
    "labix.org/v2/mgo"
)

func GetDBSession() (*mgo.Session, error) {
    session, err := mgo.Dial("localhost")

    return session, err
}

func GetDB(session *mgo.Session) *mgo.Database {
    return session.DB("test_db")
}</code>

Upon modifying cfg to use a random database, the tests passed successfully. This observation implies that tests from multiple packages run somewhat concurrently.

Possible Solution:

Option 1 (Undocumented):

• Utilize the undocumented flag go test -p 1, which builds and tests all packages sequentially.

Option 2 (Shell-Based):

• Emulate the functionality of go test ./... while enforcing sequential testing using a shell.

Bash Command:

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

Function Alias (gotest):

<code class="bash">function gotest(){   find  -name '*.go' -printf '%h\n' | sort -u | xargs -n1 -P1 go test; }</code>

By invoking gotest ., all tests in the current directory can be run sequentially.

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