type Config struct {

    // SinkAddress to dial-out to, if set.
    SinkAddress string

    // MeshConfig to use for this instance.
    MeshConfig string
}

type Instance interface {
    resource.Resource

    // Address of the Galley MCP Server.
    Address() string

    // ApplyConfig applies the given config yaml text via Galley.
    ApplyConfig(ns namespace.Instance, yamlText ...string) error

    // ApplyConfigOrFail applies the given config yaml text via Galley.
    ApplyConfigOrFail(t test.Failer, ns namespace.Instance, yamlText ...string)

    // DeleteConfig deletes the given config yaml text via Galley.
    DeleteConfig(ns namespace.Instance, yamlText ...string) error

    // DeleteConfigOrFail deletes the given config yaml text via Galley.
    DeleteConfigOrFail(t test.Failer, ns namespace.Instance, yamlText ...string)

    // ApplyConfigDir recursively applies all the config files in the specified directory
    ApplyConfigDir(ns namespace.Instance, configDir string) error

    // ClearConfig clears all applied config so far.
    ClearConfig() error

    // SetMeshConfig applies the given mesh config.
    SetMeshConfig(meshCfg string) error

    // SetMeshConfigOrFail calls SetMeshConfig and fails tests if an error is returned.
    SetMeshConfigOrFail(t test.Failer, meshCfg string)

    // WaitForSnapshot waits until the given snapshot is observed for the given type URL.
    WaitForSnapshot(collection string, validator SnapshotValidatorFunc) error

    // WaitForSnapshotOrFail calls WaitForSnapshot and fails the test if it fails.
    WaitForSnapshotOrFail(t test.Failer, collection string, validator SnapshotValidatorFunc)
}

type SnapshotObject struct {
    TypeURL  string        `protobuf:"bytes,1,opt,name=TypeURL,proto3" json:"TypeURL,omitempty"`
    Metadata *mcp.Metadata `protobuf:"bytes,2,opt,name=Metadata,proto3" json:"Metadata,omitempty"`
    Body     proto.Message `protobuf:"bytes,3,opt,name=Body,proto3" json:"Body,omitempty"`
}

type SnapshotValidatorFunc func(actuals []*SnapshotObject) error