Update Makefile and test-runner to use DOCKER_IMAGE for TiDB

- Makefile: Change testtidb targets to use DOCKER_IMAGE=tidb:VERSION format
- test-runner.go: Set DOCKER_IMAGE=tidb:VERSION for TiDB tests instead of TIDB_VERSION

Author: zph

Makefile

@@ -62,8 +62,8 @@ testcontainers-matrix: fmtcheck bin/terraform ## Run test matrix across all data
 
 # Run testcontainers tests for a specific database image
 # Usage: make testcontainers-image DOCKER_IMAGE=mysql:8.0
-#        make testcontainers-image TIDB_VERSION=8.5.3
-testcontainers-image: fmtcheck bin/terraform ## Run tests for a specific database image (set DOCKER_IMAGE or TIDB_VERSION)
+#        make testcontainers-image DOCKER_IMAGE=tidb:8.5.3
+testcontainers-image: fmtcheck bin/terraform ## Run tests for a specific database image (set DOCKER_IMAGE)
 	@PATH="$(CURDIR)/bin:${PATH}" TF_ACC=1 GOTOOLCHAIN=auto go test -tags=testcontainers $(TEST) -v $(TESTARGS) -timeout=15m
 
 bin/terraform: ## Download Terraform binary
@@ -102,10 +102,10 @@ testrdsdb: ## Run tests against Amazon RDS (requires MYSQL_ENDPOINT env vars)
 
 # TiDB test targets - use testcontainers
 testtidb%: ## Run tests against TiDB version (e.g., testtidb8.5.3)
-	@TIDB_VERSION=$* PATH="$(CURDIR)/bin:${PATH}" TF_ACC=1 GOTOOLCHAIN=auto go test -tags=testcontainers ./mysql/... -v $(if $(TESTARGS),-run "$(TESTARGS).*WithTestcontainers",-run WithTestcontainers) -timeout=30m
+	@DOCKER_IMAGE=tidb:$* PATH="$(CURDIR)/bin:${PATH}" TF_ACC=1 GOTOOLCHAIN=auto go test -tags=testcontainers ./mysql/... -v $(if $(TESTARGS),-run "$(TESTARGS).*WithTestcontainers",-run WithTestcontainers) -timeout=30m
 
 testtidb: ## Run tests against TiDB version (set MYSQL_VERSION)
-	@TIDB_VERSION=$(MYSQL_VERSION) PATH="$(CURDIR)/bin:${PATH}" TF_ACC=1 GOTOOLCHAIN=auto go test -tags=testcontainers ./mysql/... -v $(if $(TESTARGS),-run "$(TESTARGS).*WithTestcontainers",-run WithTestcontainers) -timeout=30m
+	@DOCKER_IMAGE=tidb:$(MYSQL_VERSION) PATH="$(CURDIR)/bin:${PATH}" TF_ACC=1 GOTOOLCHAIN=auto go test -tags=testcontainers ./mysql/... -v $(if $(TESTARGS),-run "$(TESTARGS).*WithTestcontainers",-run WithTestcontainers) -timeout=30m
 
 # MariaDB test targets - use testcontainers
 testmariadb%: ## Run tests against MariaDB version (e.g., testmariadb10.10)

scripts/test-runner.go

@@ -294,12 +294,15 @@ func runTest(job testJob) testResult {
 
 	// Set environment variables
 	envVars := os.Environ()
+	// All database types use DOCKER_IMAGE
+	// For TiDB, format is tidb:VERSION (e.g., tidb:6.1.7)
+	// For MySQL/Percona/MariaDB, format is already full image name (e.g., mysql:8.0)
+	dockerImage := job.image
 	if job.dbType == "TiDB" {
-		// TiDB uses version number, not full image name
-		envVars = append(envVars, "TIDB_VERSION="+job.image)
-	} else {
-		envVars = append(envVars, "DOCKER_IMAGE="+job.image)
+		// TiDB image is just version number, prepend "tidb:" prefix
+		dockerImage = "tidb:" + job.image
 	}
+	envVars = append(envVars, "DOCKER_IMAGE="+dockerImage)
 	envVars = append(envVars, "TF_ACC=1", "GOTOOLCHAIN=auto")
 	cmd.Env = envVars