Go - Varianz

The Go test integration is the varianztest package in the SDK module — no separate install:

import (
    "testing"
    "time"

    vt "go.varianz.io/sdk/varianztest"
)

func TestPriceOverride(t *testing.T) {
    session := vt.NewSession(t, "http://localhost:50051")

    session.Insert(vt.Cel("pricing/calculate-price", "42"))
    session.AwaitSyncOrFail(5 * time.Second)

    // Trigger with the session header
    resp := callService(t, "/price", body,
        map[string]string{"x-varianz-id": session.SessionID()})

    assert.Equal(t, 42.0, resp["total"])
}

vt.NewSession(t, endpoint) registers cleanup with t — stages are removed and the session destroyed when the test ends. Run go test with the standard environment (VARIANZ_ENABLED=true, and VARIANZ_INSECURE_ALLOW_PLAINTEXT=true for a plaintext local registry).

Stage examples

vt.Cel("pricing/calculate-price", "42")                              // constant override
vt.Cel("pricing/calculate-price", "invoke() * 2")                    // transform the real result
vt.Cel("pricing/calculate-price", "args.base_price + args.quantity") // read inputs
vt.Cel("pricing/calculate-price", "ctx.applyTax(invoke(), 0.1)")     // context function
vt.Cel("pricing/calculate-price", `sample("result", invoke())`)      // probe

Field names in args follow the Go SDK’s field-naming rules — BasePrice is args.base_price unless tagged otherwise.

Session API

Method	Description
`vt.NewSession(t, endpoint)`	Create a session with auto-cleanup
`SessionID()`	32-char hex session ID
`Insert(stage)`	Insert a stage (use `vt.Cel(target, expr)`)
`AwaitSync(timeout)`	Wait for subscriber confirmation, returns the result
`AwaitSyncOrFail(timeout)`	Wait; fail the test on timeout or validation failure; see zero-subscriber semantics
`AssertSample(ident)`	Start a fluent sample assertion
`Samples()`	The raw sample hub

Sample assertions

session.AssertSample("result").
    Within(10 * time.Second).
    Exists().
    HasCount(1).
    HasValue("total", 100.0)

HasValue takes a dot path into the sampled value ("" for the value itself); Samples() on the assertion returns the collected raw samples when you need custom checks.

In-process calls

When the code under test is in the same process, put the session on the context instead of a header:

ctx := varianz.WithSession(context.Background(), session.SessionID())
got, err := CalculatePrice(ctx, req)