英文:
Initialise something once for all test files, and use it in their init()
问题
我想要初始化一个数据库连接，该连接将在多个测试文件的init()函数中使用。
我希望只初始化一次数据库连接，并重复使用该连接，而不是在每个测试文件的init()函数中初始化连接。
这似乎是TestMain的一个使用案例，然而TestMain似乎在文件的init()函数之后运行（这让我感到有点奇怪，因为TestMain似乎用于对测试进行一次性全局初始化）：
type DB struct {
session string
}
var db = DB{session: "disconnected"}
func TestMain(m *testing.M) {
// 我们希望在这里初始化一次DB连接，供所有测试文件使用
db = DB{session: "connected"}
exitVal := m.Run()
os.Exit(exitVal)
}
func init() {
// 我们想要在这里使用DB连接进行一些初始化
// 我们有多个测试文件，每个文件都有一个init()函数，但它们都应该使用同一个db连接
// 不幸的是，测试文件的init()函数似乎在全局调用TestMain之后被调用
fmt.Println(db.session)
}
func TestThatNeedsDBInitializedByInitFunction(t *testing.T) {
// 需要在测试文件的init()函数中初始化DB的一些测试
}
输出（注意DB连接未初始化）：
disconnected
=== RUN TestThatNeedsDBInitializedByInitFunction
--- PASS: TestThatNeedsDBInitializedByInitFunction (0.00s)
PASS
ok github.com/fakenews/x 0.002s
鉴于我们不能使用TestMain来实现这一点，我们如何在全局范围内为所有测试文件初始化一次，并在测试文件的init()函数中使用它呢？
英文:
I want to initialize a DB connection that will be used by multiple test files in their init().
I would like to only initialize the DB connection once, and reuse the connection, instead of initializing the connection in init() in every test file.
This seemed like a use case for TestMain, however TestMain appears to run after a file's init() (which I find a bit weird given that TestMain appears to be used to do some one-off global initialization for tests):
type DB struct {
session string
}
var db = DB{session: "disconnected"}
func TestMain(m *testing.M) {
// We would like to init the DB connection once here, for all of our test files
db = DB{session: "connected"}
exitVal := m.Run()
os.Exit(exitVal)
}
func init() {
// We want to do some initialization with a DB connection here
// We have multiple test files, each with an init, but they should all use the same db
// connection
// Unfortunately, a test file's init() seems to be called _after_ TestMain is called once
// globally
fmt.Println(db.session)
}
func TestThatNeedsDBInitializedByInitFunction(t *testing.T) {
// some test that requires DB initalization in the test file's init()
}
Output (note the DB connection is not initialized):
disconnected
=== RUN TestThatNeedsDBInitializedByInitFunction
--- PASS: TestThatNeedsDBInitializedByInitFunction (0.00s)
PASS
ok github.com/fakenews/x 0.002s
Given that we can't use TestMain for this, how do we initialize something once globally for all test files in a way that we can use it in a test file's init()?
答案1
得分: 4
你可以使用立即调用的函数字面量来初始化顶层的db变量。
var db = func() DB {
// 在init()之前执行的一些连接逻辑
return DB{session: "connected"}
}()
func init() {
fmt.Println(db.session) // connected
}
链接：https://play.golang.org/p/j1LFy0n1AsG
英文:
You can initialize the top-level db variable using a function literal that you call immediately.
var db = func() DB {
// some connection logic that should be executed before init()
return DB{session: "connected"}
}()
func init() {
fmt.Println(db.session) // connected
}
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