feat: e2e testing (#75)

* feat: e2e testing boilerplate

* fix: allow custom image and version on e2e tests

* refactor: move slack fixtures to testhelper package

Prevents test utilities from being compiled and published with the
services/slack package while keeping them importable by any test.

* fix: address resource leaks, missing validation, and data correctness issues

- Terminate orphaned containers on error in Postgres and Mattermost setup
- Validate Docker Hub HTTP status before decoding response
- Add json:"-" tag to SlackChannel.Type to clarify it is computed
- Only set DeleteAt on user export when user is actually deleted

* fix: resolve gofmt and staticcheck lint errors

* rename: BasicExport -> SlackBasicExport

* e2e: added e2e tests

* chore: support GO_TEST_FLAGS in `make test`

* fix: reset cobra flags between e2e subtests to prevent state leakage

Reset all flag values and Changed state on the shared RootCmd before
each Execute() call, preventing flag pollution across subtests. Also
fix duplicate step numbering in test comments.

* fix: correct misleading test name and prevent double-close of zipWriter

- Rename test to "handles posts from multiple missing users" since no
  reactions are tested
- Add zipWriterClosed guard in wrapJSONLInZip to prevent double-close
  when tempFile.Close() fails after zipWriter.Close() succeeds

* fix: use network.WithNetworkName for correct Docker network attachment

Replace network.WithNetwork with a partial DockerNetwork struct with
the direct network.WithNetworkName call. This avoids constructing a
DockerNetwork with an empty ID field and is the idiomatic API for
attaching a container to an existing network by name.

* fix: prevent resource leak on SetupHelper failure

Register t.Cleanup(th.TearDown) immediately after creating the
TestHelper so that Docker resources are always cleaned up, even if
a later setup step (e.g. CreateMattermostContainer) calls
require.NoError and aborts before the caller's defer runs.

Make TearDown() idempotent by clearing th.tearDowns after execution
so it is safe to call from both t.Cleanup and an explicit defer.

* fix: stop logging PostgreSQL connection string with credentials

The connection string includes username and password, which would be
visible in CI logs. Replace with a generic log message.

* fix: validate full 4-byte ZIP signature in isZipFile

Only checking the first two bytes ("PK") can false-positive on
non-ZIP files. Check the full 4-byte magic for local file header
(PK\x03\x04), end of central directory (PK\x05\x06), and spanned
archive (PK\x07\x08).

* fix: normalize ZIP entry paths to forward slashes

filepath.Rel returns OS-specific separators (backslashes on Windows).
The ZIP specification requires forward slashes for entry paths.
Add filepath.ToSlash after filepath.Rel to ensure compliance.

* fix: use crypto/rand for unique team names to prevent CI collisions

time.Now().UnixNano()%10000 has only 4 digits of entropy and can
collide when parallel CI jobs run simultaneously. Replace with
crypto/rand hex suffix for reliable uniqueness.

* refactor: rename importJobMaxAttempts to importJobTimeout

The constant is used as a deadline for time.After, not as an attempt
count. With exponential backoff only ~8-10 polls actually occur.
Rename to importJobTimeout with an explicit time.Duration value and
inline the initial poll interval to make the intent clearer.

* fix: use consistent Makefile variable syntax

Replace ${GO_TEST_FLAGS} with $(GO_TEST_FLAGS) to match the $(...)
convention used everywhere else in the Makefile.

* refactor: cache allChannels() result in validate()

allChannels() was called twice, allocating two identical slices.
Store the result in a local variable and reuse it.

* refactor: consolidate transform-slack.log cleanup

Extract the log filename to a constant and use a single t.Cleanup
in each parent test function instead of repeating
defer os.Remove("transform-slack.log") in every subtest.

* fix: document why MM_SERVICESETTINGS_SITEURL uses internal address

The SiteURL env var is set to the container-internal address because
the host-mapped port is not known until after the container starts.
Add a comment explaining this is intentional and only affects
Mattermost's self-referential links, not the test API client.

* fix: add page limit to Docker Hub tag pagination loop

Guard against infinite pagination in fetchLatestStableTag by capping
at 5 pages (500 tags). This prevents the loop from running forever
if the Docker Hub API returns a malformed or circular next link.

* fix: remove unnecessary log from TestFetchLatestStableTag

The resolved tag is already validated by assertions; logging it
adds noise without aiding debugging.

* fix: guard against path traversal via channel names in SlackExportBuilder

A malformed channel name like "../../etc" would cause the export
builder to write files outside the temporary directory. Validate
that the resolved channel directory stays within the temp dir.

* fix: remove redundant defer reader.Close() in ParseSlackExportFile

The reader opened via os.Open is assigned to the same variable that
already has a defer reader.Close() registered at line 366. The extra
defer inside the USERS_JSON_FILE branch is redundant and misleading.

* fix: apply gofmt formatting to containers.go

Remove extra alignment whitespace in env map literals that was
causing golangci-lint gofmt check failures in CI.

* fix: auto-download pinned golangci-lint and handle rand.Read error

Manage golangci-lint locally in tools/bin/ pinned to v2.10.1, downloaded
automatically from GitHub releases instead of requiring a global install.
Also add a time-based fallback in uniqueTeamName when crypto/rand fails.

* add AGENTS.md with post-change checklist for CI agents

Author: fmartingr

.gitignore

@@ -13,5 +13,8 @@ tmp
 # IDE and editor files
 .idea
 
+# Locally installed tools
+tools/
+
 # OS files
 .DS_Store

AGENTS.md

@@ -0,0 +1,8 @@
+# Agents
+
+## After making code changes
+
+Always run the following before considering work complete:
+
+1. `make check-style` — linting and style checks
+2. `make test` — full test suite

Makefile

@@ -8,6 +8,24 @@ BUILD_VERSION ?= $(shell git ls-remote --tags --refs https://github.com/mattermo
 LDFLAGS += -X "github.com/mattermost/mmetl/commands.BuildHash=$(BUILD_HASH)"
 LDFLAGS += -X "github.com/mattermost/mmetl/commands.Version=$(BUILD_VERSION)"
 BUILD_COMMAND ?= go build -ldflags '$(LDFLAGS)'
+GO_TEST_FLAGS ?=
+
+GOLANGCI_LINT_VERSION ?= 2.10.1
+TOOLS_BIN := $(shell pwd)/tools/bin
+GOLANGCI_LINT := $(TOOLS_BIN)/golangci-lint
+
+UNAME_S := $(shell uname -s)
+UNAME_M := $(shell uname -m)
+ifeq ($(UNAME_S),Linux)
+  GOLANGCI_LINT_OS := linux
+else ifeq ($(UNAME_S),Darwin)
+  GOLANGCI_LINT_OS := darwin
+endif
+ifeq ($(UNAME_M),x86_64)
+  GOLANGCI_LINT_ARCH := amd64
+else ifneq (,$(filter $(UNAME_M),arm64 aarch64))
+  GOLANGCI_LINT_ARCH := arm64
+endif
 
 all: build
 
@@ -43,15 +61,17 @@ package: check-style
 
 	rm mmetl mmetl.exe
 
-golangci-lint:
-# https://stackoverflow.com/a/677212/1027058 (check if a command exists or not)
-	@if ! [ -x "$$(command -v golangci-lint)" ]; then \
-		echo "golangci-lint is not installed. Please see https://github.com/golangci/golangci-lint#install for installation instructions."; \
-		exit 1; \
-	fi; \
+$(TOOLS_BIN)/golangci-lint-v$(GOLANGCI_LINT_VERSION):
+	@mkdir -p $(TOOLS_BIN)
+	@echo "Downloading golangci-lint v$(GOLANGCI_LINT_VERSION)..."
+	@rm -f $(TOOLS_BIN)/golangci-lint-v* $(TOOLS_BIN)/golangci-lint
+	@curl -sSfL "https://github.com/golangci/golangci-lint/releases/download/v$(GOLANGCI_LINT_VERSION)/golangci-lint-$(GOLANGCI_LINT_VERSION)-$(GOLANGCI_LINT_OS)-$(GOLANGCI_LINT_ARCH).tar.gz" | tar xz -C $(TOOLS_BIN) --strip-components=1 "golangci-lint-$(GOLANGCI_LINT_VERSION)-$(GOLANGCI_LINT_OS)-$(GOLANGCI_LINT_ARCH)/golangci-lint"
+	@mv $(TOOLS_BIN)/golangci-lint $(TOOLS_BIN)/golangci-lint-v$(GOLANGCI_LINT_VERSION)
+	@ln -sf golangci-lint-v$(GOLANGCI_LINT_VERSION) $(TOOLS_BIN)/golangci-lint
 
+golangci-lint: $(TOOLS_BIN)/golangci-lint-v$(GOLANGCI_LINT_VERSION)
 	@echo Running golangci-lint
-	golangci-lint run ./...
+	$(GOLANGCI_LINT) run ./...
 
 gofmt:
 	@echo Running gofmt
@@ -71,7 +91,7 @@ gofmt:
 
 test:
 	@echo Running tests
-	$(GO) test -race -v $(GO_PACKAGES) -count=1
+	$(GO) test -race -v $(GO_PACKAGES) -count=1 $(GO_TEST_FLAGS)
 
 check-style: golangci-lint