test(storage): Replace handwritten storage mocks with gomock bazel rule

CLAUDE.md

@@ -184,6 +184,61 @@ make clean              # Clean Bazel cache
 **Add new entity:**
 1. Create `entity/{domain}/{entity}.go` with test file and `BUILD.bazel`
 
+**Add gomock for an extension interface:**
+
+Mocks use the Bazel `gomock` rule from `@rules_go//extras:gomock.bzl` and are generated at build time (not checked in). See `extension/storage/mock/` for the canonical example.
+
+To add a mock for a new interface file in an existing mock package (e.g., `extension/storage/new_store.go`):
+
+1. Add a `//go:generate` directive to the interface file:
+   ```go
+   //go:generate mockgen -source=new_store.go -destination=mock/new_store.go -package=mock
+   ```
+2. Add the file to `exports_files` in the parent `BUILD.bazel` with visibility to the mock package:
+   ```starlark
+   exports_files(
+       ["new_store.go", ...],
+       visibility = ["//extension/storage/mock:__pkg__"],
+   )
+   ```
+3. Add a `gomock` rule in the mock `BUILD.bazel`:
+   ```starlark
+   gomock(
+       name = "mock_new_store_src",
+       out = "new_store_mock.go",
+       mockgen_tool = _MOCKGEN,
+       package = "mock",
+       source = "//extension/storage:new_store.go",
+       source_importpath = "github.com/uber/submitqueue/extension/storage",
+   )
+   ```
+4. Add the rule target to the `go_library` srcs in the same file.
+
+To create a mock package for a new extension (e.g., `extension/queue/mock/`):
+
+1. Create `extension/{ext}/mock/BUILD.bazel` with `gomock` rules, a `go_library`, and `# gazelle:ignore`.
+2. Add `exports_files` to `extension/{ext}/BUILD.bazel` for each interface file.
+3. Follow the same per-interface pattern as above.
+
+Mock `BUILD.bazel` files use `# gazelle:ignore` so `make gazelle` will not update them — they must be maintained manually.
+
+**Using mocks in tests:**
+```go
+import storagemock "github.com/uber/submitqueue/extension/storage/mock"
+
+ctrl := gomock.NewController(t)
+mockStore := storagemock.NewMockRequestStore(ctrl)
+mockStore.EXPECT().Create(gomock.Any(), gomock.Any()).Return(nil)
+```
+
+Test `BUILD.bazel` deps:
+```starlark
+deps = [
+    "//extension/storage/mock",
+    "@org_uber_go_mock//gomock",
+]
+```
+
 ### Testing
 
 - **Table-driven tests** — prefer table-driven tests with `t.Run` subtests over individual test functions.

extension/storage/BUILD.bazel

@@ -1,5 +1,18 @@
 load("@rules_go//go:def.bzl", "go_library")
 
+exports_files(
+    [
+        "batch_dependent_store.go",
+        "batch_store.go",
+        "build_store.go",
+        "change_provider_store.go",
+        "request_store.go",
+        "speculation_tree_store.go",
+        "storage.go",
+    ],
+    visibility = ["//extension/storage/mock:__pkg__"],
+)
+
 go_library(
     name = "storage",
     srcs = [

extension/storage/batch_dependent_store.go

@@ -1,5 +1,7 @@
 package storage
 
+//go:generate mockgen -source=batch_dependent_store.go -destination=mock/batch_dependent_store.go -package=mock
+
 import (
 	"context"
 

extension/storage/batch_store.go

@@ -1,5 +1,7 @@
 package storage
 
+//go:generate mockgen -source=batch_store.go -destination=mock/batch_store.go -package=mock
+
 import (
 	"context"
 

extension/storage/build_store.go

@@ -1,5 +1,7 @@
 package storage
 
+//go:generate mockgen -source=build_store.go -destination=mock/build_store.go -package=mock
+
 import (
 	"context"
 

extension/storage/change_provider_store.go

@@ -1,5 +1,7 @@
 package storage
 
+//go:generate mockgen -source=change_provider_store.go -destination=mock/change_provider_store.go -package=mock
+
 import (
 	"context"
 

extension/storage/mock/BUILD.bazel

@@ -0,0 +1,88 @@
+load("@rules_go//extras:gomock.bzl", "gomock")
+load("@rules_go//go:def.bzl", "go_library")
+
+_MOCKGEN = "@org_uber_go_mock//mockgen"
+
+gomock(
+    name = "mock_storage_src",
+    out = "storage_mock.go",
+    mockgen_tool = _MOCKGEN,
+    package = "mock",
+    source = "//extension/storage:storage.go",
+    source_importpath = "github.com/uber/submitqueue/extension/storage",
+)
+
+gomock(
+    name = "mock_request_store_src",
+    out = "request_store_mock.go",
+    mockgen_tool = _MOCKGEN,
+    package = "mock",
+    source = "//extension/storage:request_store.go",
+    source_importpath = "github.com/uber/submitqueue/extension/storage",
+)
+
+gomock(
+    name = "mock_change_provider_store_src",
+    out = "change_provider_store_mock.go",
+    mockgen_tool = _MOCKGEN,
+    package = "mock",
+    source = "//extension/storage:change_provider_store.go",
+    source_importpath = "github.com/uber/submitqueue/extension/storage",
+)
+
+gomock(
+    name = "mock_batch_store_src",
+    out = "batch_store_mock.go",
+    mockgen_tool = _MOCKGEN,
+    package = "mock",
+    source = "//extension/storage:batch_store.go",
+    source_importpath = "github.com/uber/submitqueue/extension/storage",
+)
+
+gomock(
+    name = "mock_batch_dependent_store_src",
+    out = "batch_dependent_store_mock.go",
+    mockgen_tool = _MOCKGEN,
+    package = "mock",
+    source = "//extension/storage:batch_dependent_store.go",
+    source_importpath = "github.com/uber/submitqueue/extension/storage",
+)
+
+gomock(
+    name = "mock_build_store_src",
+    out = "build_store_mock.go",
+    mockgen_tool = _MOCKGEN,
+    package = "mock",
+    source = "//extension/storage:build_store.go",
+    source_importpath = "github.com/uber/submitqueue/extension/storage",
+)
+
+gomock(
+    name = "mock_speculation_tree_store_src",
+    out = "speculation_tree_store_mock.go",
+    mockgen_tool = _MOCKGEN,
+    package = "mock",
+    source = "//extension/storage:speculation_tree_store.go",
+    source_importpath = "github.com/uber/submitqueue/extension/storage",
+)
+
+# gazelle:ignore
+go_library(
+    name = "mock",
+    srcs = [
+        ":mock_batch_dependent_store_src",
+        ":mock_batch_store_src",
+        ":mock_build_store_src",
+        ":mock_change_provider_store_src",
+        ":mock_request_store_src",
+        ":mock_speculation_tree_store_src",
+        ":mock_storage_src",
+    ],
+    importpath = "github.com/uber/submitqueue/extension/storage/mock",
+    visibility = ["//visibility:public"],
+    deps = [
+        "//entity",
+        "//extension/storage",
+        "@org_uber_go_mock//gomock",
+    ],
+)

extension/storage/mock/README.md

@@ -0,0 +1,42 @@
+# Storage Mocks
+
+Generated mocks for all `extension/storage` interfaces using [gomock](https://github.com/uber-go/mock).
+
+Mocks are **not checked in** — they are generated at build time by the Bazel `gomock` rule.
+
+## Adding a new store interface
+
+When a new store interface file is added to `extension/storage/`:
+
+1. Add a `//go:generate` directive to the new file:
+   ```go
+   //go:generate mockgen -source=new_store.go -destination=mock/new_store.go -package=mock
+   ```
+
+2. Add the file to `exports_files` in `extension/storage/BUILD.bazel`.
+
+3. Add a new `gomock` rule in `extension/storage/mock/BUILD.bazel`:
+   ```starlark
+   gomock(
+       name = "mock_new_store_src",
+       out = "new_store_mock.go",
+       mockgen_tool = _MOCKGEN,
+       package = "mock",
+       source = "//extension/storage:new_store.go",
+       source_importpath = "github.com/uber/submitqueue/extension/storage",
+   )
+   ```
+
+4. Add the new rule target to the `go_library` srcs in the same file:
+   ```starlark
+   go_library(
+       name = "mock",
+       srcs = [
+           ...
+           ":mock_new_store_src",
+       ],
+       ...
+   )
+   ```
+
+> **Note:** This BUILD.bazel uses `# gazelle:ignore`, so gazelle will not update it automatically.

extension/storage/request_store.go

@@ -1,5 +1,7 @@
 package storage
 
+//go:generate mockgen -source=request_store.go -destination=mock/request_store.go -package=mock
+
 import (
 	"context"
 

extension/storage/speculation_tree_store.go

@@ -1,5 +1,7 @@
 package storage
 
+//go:generate mockgen -source=speculation_tree_store.go -destination=mock/speculation_tree_store.go -package=mock
+
 import (
 	"context"
 

extension/storage/storage.go

@@ -1,5 +1,7 @@
 package storage
 
+//go:generate mockgen -source=storage.go -destination=mock/storage.go -package=mock
+
 import "errors"
 import "fmt"
 

gateway/controller/BUILD.bazel

@@ -30,11 +30,12 @@ go_test(
     deps = [
         "//entity",
         "//entity/queue",
-        "//extension/storage",
+        "//extension/storage/mock",
         "//gateway/protopb",
         "@com_github_stretchr_testify//assert",
         "@com_github_stretchr_testify//require",
         "@com_github_uber_go_tally_v4//:tally",
+        "@org_uber_go_mock//gomock",
         "@org_uber_go_zap//:zap",
     ],
 )