diff --git a/backend/controller/admin/local_client_test.go b/backend/controller/admin/local_client_test.go
index 1d4f9eab4..97e0a66e5 100644
--- a/backend/controller/admin/local_client_test.go
+++ b/backend/controller/admin/local_client_test.go
@@ -6,15 +6,18 @@ import (
 	"context"
 	"testing"
 
+	"github.com/alecthomas/assert/v2"
+	"github.com/alecthomas/types/optional"
+
 	cf "github.com/TBD54566975/ftl/common/configuration"
 	in "github.com/TBD54566975/ftl/integration"
 	"github.com/TBD54566975/ftl/internal/log"
-	"github.com/alecthomas/assert/v2"
-	"github.com/alecthomas/types/optional"
 )
 
 func TestDiskSchemaRetrieverWithBuildArtefact(t *testing.T) {
-	in.RunWithoutController(t, "ftl-project-dr.toml",
+	in.Run(t,
+		in.WithFTLConfig("ftl-project-dr.toml"),
+		in.WithoutController(),
 		in.CopyModule("dischema"),
 		in.Build("dischema"),
 		func(t testing.TB, ic in.TestContext) {
@@ -30,7 +33,9 @@ func TestDiskSchemaRetrieverWithBuildArtefact(t *testing.T) {
 }
 
 func TestDiskSchemaRetrieverWithNoSchema(t *testing.T) {
-	in.RunWithoutController(t, "ftl-project-dr.toml",
+	in.Run(t,
+		in.WithFTLConfig("ftl-project-dr.toml"),
+		in.WithoutController(),
 		in.CopyModule("dischema"),
 		func(t testing.TB, ic in.TestContext) {
 			dsr := &diskSchemaRetriever{}
diff --git a/backend/controller/console/console_integration_test.go b/backend/controller/console/console_integration_test.go
index b3d1baa88..22513f361 100644
--- a/backend/controller/console/console_integration_test.go
+++ b/backend/controller/console/console_integration_test.go
@@ -6,9 +6,10 @@ import (
 	"testing"
 
 	"connectrpc.com/connect"
+	"github.com/alecthomas/assert/v2"
+
 	pbconsole "github.com/TBD54566975/ftl/backend/protos/xyz/block/ftl/v1/console"
 	in "github.com/TBD54566975/ftl/integration"
-	"github.com/alecthomas/assert/v2"
 )
 
 // GetModules calls console service GetModules and returns the response.
@@ -24,7 +25,7 @@ func GetModules(onResponse func(t testing.TB, resp *connect.Response[pbconsole.G
 }
 
 func TestConsoleGetModules(t *testing.T) {
-	in.Run(t, "",
+	in.Run(t,
 		in.CopyModule("console"),
 		in.Deploy("console"),
 		GetModules(func(t testing.TB, resp *connect.Response[pbconsole.GetModulesResponse]) {
diff --git a/backend/controller/cronjobs/cronjobs_integration_test.go b/backend/controller/cronjobs/cronjobs_integration_test.go
index 62d9984c5..5824acbbf 100644
--- a/backend/controller/cronjobs/cronjobs_integration_test.go
+++ b/backend/controller/cronjobs/cronjobs_integration_test.go
@@ -53,7 +53,7 @@ func TestCron(t *testing.T) {
 
 	t.Cleanup(func() { _ = os.Remove(tmpFile) })
 
-	in.Run(t, "",
+	in.Run(t,
 		in.CopyModule("cron"),
 		in.Deploy("cron"),
 		func(t testing.TB, ic in.TestContext) {
diff --git a/backend/controller/dal/fsm_integration_test.go b/backend/controller/dal/fsm_integration_test.go
index 6ae5a00e8..2fee9701c 100644
--- a/backend/controller/dal/fsm_integration_test.go
+++ b/backend/controller/dal/fsm_integration_test.go
@@ -8,8 +8,9 @@ import (
 	"testing"
 	"time"
 
-	in "github.com/TBD54566975/ftl/integration"
 	"github.com/alecthomas/assert/v2"
+
+	in "github.com/TBD54566975/ftl/integration"
 )
 
 func TestFSM(t *testing.T) {
@@ -22,7 +23,7 @@ func TestFSM(t *testing.T) {
 			WHERE fsm = 'fsm.fsm' AND key = '%s'
 		`, instance), status, state)
 	}
-	in.Run(t, "",
+	in.Run(t,
 		in.CopyModule("fsm"),
 		in.Deploy("fsm"),
 
@@ -81,7 +82,7 @@ func TestFSMRetry(t *testing.T) {
 		}
 	}
 
-	in.Run(t, "",
+	in.Run(t,
 		in.CopyModule("fsmretry"),
 		in.Build("fsmretry"),
 		in.Deploy("fsmretry"),
@@ -127,7 +128,7 @@ func TestFSMRetry(t *testing.T) {
 func TestFSMGoTests(t *testing.T) {
 	logFilePath := filepath.Join(t.TempDir(), "fsm.log")
 	t.Setenv("FSM_LOG_FILE", logFilePath)
-	in.Run(t, "",
+	in.Run(t,
 		in.CopyModule("fsm"),
 		in.Build("fsm"),
 		in.ExecModuleTest("fsm"),
diff --git a/backend/controller/ingress/ingress_integration_test.go b/backend/controller/ingress/ingress_integration_test.go
index e5474d314..4679ce16a 100644
--- a/backend/controller/ingress/ingress_integration_test.go
+++ b/backend/controller/ingress/ingress_integration_test.go
@@ -14,7 +14,7 @@ import (
 )
 
 func TestHttpIngress(t *testing.T) {
-	in.Run(t, "",
+	in.Run(t,
 		in.CopyModule("httpingress"),
 		in.Deploy("httpingress"),
 		in.HttpCall(http.MethodGet, "/users/123/posts/456", nil, in.JsonData(t, in.Obj{}), func(t testing.TB, resp *in.HTTPResponse) {
@@ -152,7 +152,7 @@ func TestHttpIngress(t *testing.T) {
 func TestHttpIngressWithCors(t *testing.T) {
 	os.Setenv("FTL_CONTROLLER_ALLOW_ORIGIN", "http://localhost:8892")
 	os.Setenv("FTL_CONTROLLER_ALLOW_HEADERS", "x-forwarded-capabilities")
-	in.Run(t, "",
+	in.Run(t,
 		in.CopyModule("httpingress"),
 		in.Deploy("httpingress"),
 		// A correct CORS preflight request
diff --git a/backend/controller/leases/lease_integration_test.go b/backend/controller/leases/lease_integration_test.go
index 002fb62f6..3af001258 100644
--- a/backend/controller/leases/lease_integration_test.go
+++ b/backend/controller/leases/lease_integration_test.go
@@ -18,7 +18,7 @@ import (
 )
 
 func TestLease(t *testing.T) {
-	in.Run(t, "",
+	in.Run(t,
 		in.CopyModule("leases"),
 		in.Build("leases"),
 		// checks if leases work in a unit test environment
diff --git a/backend/controller/pubsub/integration_test.go b/backend/controller/pubsub/integration_test.go
index bc8dbdd0b..879db011d 100644
--- a/backend/controller/pubsub/integration_test.go
+++ b/backend/controller/pubsub/integration_test.go
@@ -15,7 +15,7 @@ import (
 func TestPubSub(t *testing.T) {
 	calls := 20
 	events := calls * 10
-	in.Run(t, "",
+	in.Run(t,
 		in.CopyModule("publisher"),
 		in.CopyModule("subscriber"),
 		in.Deploy("publisher"),
@@ -40,7 +40,7 @@ func TestPubSub(t *testing.T) {
 }
 
 func TestConsumptionDelay(t *testing.T) {
-	in.Run(t, "",
+	in.Run(t,
 		in.CopyModule("publisher"),
 		in.CopyModule("subscriber"),
 		in.Deploy("publisher"),
@@ -83,7 +83,7 @@ func TestConsumptionDelay(t *testing.T) {
 
 func TestRetry(t *testing.T) {
 	retriesPerCall := 2
-	in.Run(t, "",
+	in.Run(t,
 		in.CopyModule("publisher"),
 		in.CopyModule("subscriber"),
 		in.Deploy("publisher"),
@@ -135,7 +135,7 @@ func TestRetry(t *testing.T) {
 }
 
 func TestExternalPublishRuntimeCheck(t *testing.T) {
-	in.Run(t, "",
+	in.Run(t,
 		in.CopyModule("publisher"),
 		in.CopyModule("subscriber"),
 		in.Deploy("publisher"),
diff --git a/backend/controller/sql/database_integration_test.go b/backend/controller/sql/database_integration_test.go
index 57e355beb..a82cdb84b 100644
--- a/backend/controller/sql/database_integration_test.go
+++ b/backend/controller/sql/database_integration_test.go
@@ -10,7 +10,8 @@ import (
 )
 
 func TestDatabase(t *testing.T) {
-	in.Run(t, "database/ftl-project.toml",
+	in.Run(t,
+		in.WithFTLConfig("database/ftl-project.toml"),
 		// deploy real module against "testdb"
 		in.CopyModule("database"),
 		in.CreateDBAction("database", "testdb", false),
@@ -33,7 +34,8 @@ func TestMigrate(t *testing.T) {
 		return in.QueryRow(dbName, "SELECT version FROM schema_migrations WHERE version = '20240704103403'", "20240704103403")
 	}
 
-	in.RunWithoutController(t, "",
+	in.Run(t,
+		in.WithoutController(),
 		in.DropDBAction(t, dbName),
 		in.Fail(q(), "Should fail because the database does not exist."),
 		in.Exec("ftl", "migrate", "--dsn", dbUri),
diff --git a/cmd/ftl/integration_test.go b/cmd/ftl/integration_test.go
index 015fa07e2..75b19e426 100644
--- a/cmd/ftl/integration_test.go
+++ b/cmd/ftl/integration_test.go
@@ -24,7 +24,8 @@ func TestBox(t *testing.T) {
 	ctx := log.ContextWithNewDefaultLogger(context.Background())
 	err := exec.Command(ctx, log.Debug, "../..", "docker", "build", "-t", "ftl0/ftl-box:latest", "--progress=plain", "--platform=linux/amd64", "-f", "Dockerfile.box", ".").Run()
 	assert.NoError(t, err)
-	RunWithoutController(t, "",
+	Run(t,
+		WithoutController(),
 		CopyModule("time"),
 		CopyModule("echo"),
 		Exec("ftl", "box", "echo", "--compose=echo-compose.yml"),
@@ -35,17 +36,17 @@ func TestBox(t *testing.T) {
 }
 
 func TestConfigsWithController(t *testing.T) {
-	Run(t, "", configActions(t)...)
+	Run(t, configActions(t)...)
 }
 
 func TestConfigsWithoutController(t *testing.T) {
-	RunWithoutController(t, "", configActions(t)...)
+	Run(t, configActions(t, WithoutController())...)
 }
 
-func configActions(t *testing.T) []Action {
+func configActions(t *testing.T, prepend ...ActionOrOption) []ActionOrOption {
 	t.Helper()
 
-	return []Action{
+	return append(prepend,
 		// test setting value without --json flag
 		Exec("ftl", "config", "set", "test.one", "hello world", "--inline"),
 		ExecWithExpectedOutput("\"hello world\"\n", "ftl", "config", "get", "test.one"),
@@ -58,18 +59,18 @@ func configActions(t *testing.T) []Action {
 			ExecWithOutput("ftl", []string{"config", "get", "test.one"}, func(output string) {}),
 			"failed to get from config manager: not found",
 		),
-	}
+	)
 }
 
 func TestSecretsWithController(t *testing.T) {
-	Run(t, "", secretActions(t)...)
+	Run(t, secretActions(t)...)
 }
 
 func TestSecretsWithoutController(t *testing.T) {
-	RunWithoutController(t, "", secretActions(t)...)
+	Run(t, secretActions(t, WithoutController())...)
 }
 
-func secretActions(t *testing.T) []Action {
+func secretActions(t *testing.T, prepend ...ActionOrOption) []ActionOrOption {
 	t.Helper()
 
 	// can not easily use Exec() to enter secure text, using secret import instead
@@ -78,7 +79,7 @@ func secretActions(t *testing.T) []Action {
 	secretsPath2, err := filepath.Abs("testdata/secrets2.json")
 	assert.NoError(t, err)
 
-	return []Action{
+	return append(prepend,
 		// test setting secret without --json flag
 		Exec("ftl", "secret", "import", "--inline", secretsPath1),
 		ExecWithExpectedOutput("\"hello world\"\n", "ftl", "secret", "get", "test.one"),
@@ -91,7 +92,7 @@ func secretActions(t *testing.T) []Action {
 			ExecWithOutput("ftl", []string{"secret", "get", "test.one"}, func(output string) {}),
 			"failed to get from secret manager: not found",
 		),
-	}
+	)
 }
 
 func TestSecretImportExport(t *testing.T) {
@@ -116,7 +117,8 @@ func testImportExport(t *testing.T, object string) {
 	blank := ""
 	exported := &blank
 
-	RunWithoutController(t, "",
+	Run(t,
+		WithoutController(),
 		// duplicate project file in the temp directory
 		Exec("cp", firstProjFile, secondProjFile),
 		// import into first project file
@@ -152,7 +154,7 @@ func NewFunction(ctx context.Context, req TimeRequest) (TimeResponse, error) {
 	return TimeResponse{Time: time.Now()}, nil
 }
 `
-	Run(t, "",
+	Run(t,
 		CopyModule("time"),
 		Deploy("time"),
 		ExecWithOutput("ftl", []string{"schema", "diff"}, func(output string) {
@@ -199,7 +201,7 @@ func TestResetSubscription(t *testing.T) {
 		`, module, subscription), cursor)
 	}
 
-	Run(t, "",
+	Run(t,
 		CopyModule("time"),
 		CopyModule("echo"),
 		Deploy("time"),
diff --git a/common/projectconfig/integration_test.go b/common/projectconfig/integration_test.go
index 2e79d26e3..f7b46df8d 100644
--- a/common/projectconfig/integration_test.go
+++ b/common/projectconfig/integration_test.go
@@ -14,7 +14,8 @@ import (
 )
 
 func TestDefaultToRootWhenModuleDirsMissing(t *testing.T) {
-	in.Run(t, "no-module-dirs-ftl-project.toml",
+	in.Run(t,
+		in.WithFTLConfig("no-module-dirs-ftl-project.toml"),
 		in.CopyModule("echo"),
 		in.Exec("ftl", "build"), // Needs to be `ftl build`, not `ftl build echo`
 		in.Deploy("echo"),
@@ -25,7 +26,9 @@ func TestDefaultToRootWhenModuleDirsMissing(t *testing.T) {
 }
 
 func TestConfigCmdWithoutController(t *testing.T) {
-	in.RunWithoutController(t, "configs-ftl-project.toml",
+	in.Run(t,
+		in.WithFTLConfig("configs-ftl-project.toml"),
+		in.WithoutController(),
 		in.ExecWithExpectedOutput("\"value\"\n", "ftl", "config", "get", "key"),
 	)
 }
@@ -49,7 +52,8 @@ func TestFindConfig(t *testing.T) {
 			assert.Equal(t, "test = \"test\"\n", string(output))
 		}
 	}
-	in.RunWithoutController(t, "",
+	in.Run(t,
+		in.WithoutController(),
 		in.CopyModule("findconfig"),
 		checkConfig("findconfig"),
 		checkConfig("findconfig/subdir"),
@@ -61,7 +65,8 @@ func TestFindConfig(t *testing.T) {
 }
 
 func TestConfigValidation(t *testing.T) {
-	in.Run(t, "./validateconfig/ftl-project.toml",
+	in.Run(t,
+		in.WithFTLConfig("./validateconfig/ftl-project.toml"),
 		in.CopyModule("validateconfig"),
 
 		// Global sets never error.
diff --git a/go-runtime/compile/compile_integration_test.go b/go-runtime/compile/compile_integration_test.go
index 567eca4cc..23091bbfd 100644
--- a/go-runtime/compile/compile_integration_test.go
+++ b/go-runtime/compile/compile_integration_test.go
@@ -12,7 +12,7 @@ import (
 )
 
 func TestNonExportedDecls(t *testing.T) {
-	in.Run(t, "",
+	in.Run(t,
 		in.CopyModule("time"),
 		in.Deploy("time"),
 		in.CopyModule("echo"),
@@ -26,7 +26,7 @@ func TestNonExportedDecls(t *testing.T) {
 }
 
 func TestUndefinedExportedDecls(t *testing.T) {
-	in.Run(t, "",
+	in.Run(t,
 		in.CopyModule("time"),
 		in.Deploy("time"),
 		in.CopyModule("echo"),
@@ -40,7 +40,7 @@ func TestUndefinedExportedDecls(t *testing.T) {
 }
 
 func TestNonFTLTypes(t *testing.T) {
-	in.Run(t, "",
+	in.Run(t,
 		in.CopyModule("external"),
 		in.Deploy("external"),
 		in.Call("external", "echo", in.Obj{"message": "hello"}, func(t testing.TB, response in.Obj) {
@@ -50,7 +50,7 @@ func TestNonFTLTypes(t *testing.T) {
 }
 
 func TestNonStructRequestResponse(t *testing.T) {
-	in.Run(t, "",
+	in.Run(t,
 		in.CopyModule("two"),
 		in.Deploy("two"),
 		in.CopyModule("one"),
diff --git a/go-runtime/encoding/encoding_integration_test.go b/go-runtime/encoding/encoding_integration_test.go
index d8157ba36..35cfa1586 100644
--- a/go-runtime/encoding/encoding_integration_test.go
+++ b/go-runtime/encoding/encoding_integration_test.go
@@ -6,12 +6,13 @@ import (
 	"net/http"
 	"testing"
 
-	in "github.com/TBD54566975/ftl/integration"
 	"github.com/alecthomas/assert/v2"
+
+	in "github.com/TBD54566975/ftl/integration"
 )
 
 func TestHttpEncodeOmitempty(t *testing.T) {
-	in.Run(t, "",
+	in.Run(t,
 		in.CopyModule("omitempty"),
 		in.Deploy("omitempty"),
 		in.HttpCall(http.MethodGet, "/get", nil, in.JsonData(t, in.Obj{}), func(t testing.TB, resp *in.HTTPResponse) {
diff --git a/go-runtime/ftl/ftl_integration_test.go b/go-runtime/ftl/ftl_integration_test.go
index 06afc15ae..1dff86c46 100644
--- a/go-runtime/ftl/ftl_integration_test.go
+++ b/go-runtime/ftl/ftl_integration_test.go
@@ -6,14 +6,15 @@ import (
 	"strings"
 	"testing"
 
-	in "github.com/TBD54566975/ftl/integration"
 	"github.com/alecthomas/assert/v2"
 
+	in "github.com/TBD54566975/ftl/integration"
+
 	"github.com/alecthomas/repr"
 )
 
 func TestLifecycle(t *testing.T) {
-	in.Run(t, "",
+	in.Run(t,
 		in.GitInit(),
 		in.Exec("rm", "ftl-project.toml"),
 		in.Exec("ftl", "init", "test", "."),
@@ -26,7 +27,7 @@ func TestLifecycle(t *testing.T) {
 }
 
 func TestInterModuleCall(t *testing.T) {
-	in.Run(t, "",
+	in.Run(t,
 		in.CopyModule("echo"),
 		in.CopyModule("time"),
 		in.Deploy("time"),
@@ -42,7 +43,7 @@ func TestInterModuleCall(t *testing.T) {
 }
 
 func TestSchemaGenerate(t *testing.T) {
-	in.Run(t, "",
+	in.Run(t,
 		in.CopyDir("../schema-generate", "schema-generate"),
 		in.Mkdir("build/schema-generate"),
 		in.Exec("ftl", "schema", "generate", "schema-generate", "build/schema-generate"),
@@ -51,7 +52,7 @@ func TestSchemaGenerate(t *testing.T) {
 }
 
 func TestTypeRegistryUnitTest(t *testing.T) {
-	in.Run(t, "",
+	in.Run(t,
 		in.CopyModule("typeregistry"),
 		in.Deploy("typeregistry"),
 		in.ExecModuleTest("typeregistry"),
diff --git a/go-runtime/ftl/ftltest/ftltest_integration_test.go b/go-runtime/ftl/ftltest/ftltest_integration_test.go
index d53a8cf0d..5eb88500d 100644
--- a/go-runtime/ftl/ftltest/ftltest_integration_test.go
+++ b/go-runtime/ftl/ftltest/ftltest_integration_test.go
@@ -9,7 +9,9 @@ import (
 )
 
 func TestModuleUnitTests(t *testing.T) {
-	in.RunWithoutController(t, "wrapped/ftl-project.toml",
+	in.Run(t,
+		in.WithFTLConfig("wrapped/ftl-project.toml"),
+		in.WithoutController(),
 		in.GitInit(),
 		in.CopyModule("time"),
 		in.CopyModule("wrapped"),
diff --git a/go-runtime/ftl/integration_test.go b/go-runtime/ftl/integration_test.go
index 155156a76..e96d0ff0f 100644
--- a/go-runtime/ftl/integration_test.go
+++ b/go-runtime/ftl/integration_test.go
@@ -9,7 +9,7 @@ import (
 )
 
 func TestFTLMap(t *testing.T) {
-	in.Run(t, "",
+	in.Run(t,
 		in.CopyModule("mapper"),
 		in.Build("mapper"),
 		in.ExecModuleTest("mapper"),
diff --git a/go-runtime/ftl/reflection/reflection_integration_test.go b/go-runtime/ftl/reflection/reflection_integration_test.go
index e858feefc..c91c9fdef 100644
--- a/go-runtime/ftl/reflection/reflection_integration_test.go
+++ b/go-runtime/ftl/reflection/reflection_integration_test.go
@@ -9,7 +9,7 @@ import (
 )
 
 func TestRuntimeReflection(t *testing.T) {
-	in.Run(t, "",
+	in.Run(t,
 		in.CopyModule("runtimereflection"),
 		in.ExecModuleTest("runtimereflection"),
 	)
diff --git a/go-runtime/internal/integration_test.go b/go-runtime/internal/integration_test.go
index 9c7f07b56..5f2bca228 100644
--- a/go-runtime/internal/integration_test.go
+++ b/go-runtime/internal/integration_test.go
@@ -11,7 +11,7 @@ import (
 )
 
 func TestRealMap(t *testing.T) {
-	Run(t, "",
+	Run(t,
 		CopyModule("mapper"),
 		Deploy("mapper"),
 		Call("mapper", "get", Obj{}, func(t testing.TB, response Obj) {
diff --git a/integration/actions.go b/integration/actions.go
index ebfe57d40..7875fd742 100644
--- a/integration/actions.go
+++ b/integration/actions.go
@@ -51,13 +51,18 @@ func GitInit() Action {
 
 // Copy a module from the testdata directory to the working directory.
 //
-// Ensures that replace directives are correctly handled.
+// Ensures that any language-specific local modifications are made correctly,
+// such as Go module file replace directives for FTL.
 func CopyModule(module string) Action {
 	return Chain(
 		CopyDir(module, module),
 		func(t testing.TB, ic TestContext) {
-			err := ftlexec.Command(ic, log.Debug, filepath.Join(ic.workDir, module), "go", "mod", "edit", "-replace", "github.com/TBD54566975/ftl="+ic.RootDir).RunBuffered(ic)
-			assert.NoError(t, err)
+			root := filepath.Join(ic.workDir, module)
+			// TODO: Load the module configuration from the module itself and use that to determine the language-specific stuff.
+			if _, err := os.Stat(filepath.Join(root, "go.mod")); err == nil {
+				err := ftlexec.Command(ic, log.Debug, root, "go", "mod", "edit", "-replace", "github.com/TBD54566975/ftl="+ic.RootDir).RunBuffered(ic)
+				assert.NoError(t, err)
+			}
 		},
 	)
 }
diff --git a/integration/harness.go b/integration/harness.go
index 5a9281ec5..b9a192ecc 100644
--- a/integration/harness.go
+++ b/integration/harness.go
@@ -43,47 +43,98 @@ func Infof(format string, args ...any) {
 
 var buildOnce sync.Once
 
-// Run an integration test.
-// ftlConfigPath: if FTL_CONFIG should be set for this test, then pass in the relative
+// An Option for configuring the integration test harness.
+type Option func(*options)
+
+// ActionOrOption is a type that can be either an Action or an Option.
+type ActionOrOption any
+
+// WithLanguages is a Run* option that specifies the languages to test.
 //
-//	path based on ./testdata/go/ where "." denotes the directory containing the
-//	integration test (e.g. for "integration/harness_test.go" supplying
-//	"database/ftl-project.toml" would set FTL_CONFIG to
-//	"integration/testdata/go/database/ftl-project.toml").
-func Run(t *testing.T, ftlConfigPath string, actions ...Action) {
-	run(t, ftlConfigPath, true, false, actions...)
+// Defaults to "go" if not provided.
+func WithLanguages(languages ...string) Option {
+	return func(o *options) {
+		o.languages = languages
+	}
 }
 
-// RunWithJava runs an integration test after building the Java runtime.
-// ftlConfigPath: if FTL_CONFIG should be set for this test, then pass in the relative
+// WithFTLConfig is a Run* option that specifies the FTL config to use.
 //
-//	path based on ./testdata/go/ where "." denotes the directory containing the
-//	integration test (e.g. for "integration/harness_test.go" supplying
-//	"database/ftl-project.toml" would set FTL_CONFIG to
-//	"integration/testdata/go/database/ftl-project.toml").
-func RunWithJava(t *testing.T, ftlConfigPath string, actions ...Action) {
-	run(t, ftlConfigPath, true, true, actions...)
+// This will set FTL_CONFIG for this test, then pass in the relative
+// path based on ./testdata/go/ where "." denotes the directory containing the
+// integration test (e.g. for "integration/harness_test.go" supplying
+// "database/ftl-project.toml" would set FTL_CONFIG to
+// "integration/testdata/go/database/ftl-project.toml").
+func WithFTLConfig(path string) Option {
+	return func(o *options) {
+		o.ftlConfigPath = path
+	}
 }
 
-// RunWithoutController runs an integration test without starting the controller.
-// ftlConfigPath: if FTL_CONFIG should be set for this test, then pass in the relative
-//
-//	path based on ./testdata/go/ where "." denotes the directory containing the
-//	integration test (e.g. for "integration/harness_test.go" supplying
-//	"database/ftl-project.toml" would set FTL_CONFIG to
-//	"integration/testdata/go/database/ftl-project.toml").
-func RunWithoutController(t *testing.T, ftlConfigPath string, actions ...Action) {
-	run(t, ftlConfigPath, false, false, actions...)
+// WithEnvar is a Run* option that specifies an environment variable to set.
+func WithEnvar(key, value string) Option {
+	return func(o *options) {
+		o.envars[key] = value
+	}
 }
 
-func RunWithEncryption(t *testing.T, ftlConfigPath string, actions ...Action) {
-	uri := "fake-kms://CKbvh_ILElQKSAowdHlwZS5nb29nbGVhcGlzLmNvbS9nb29nbGUuY3J5cHRvLnRpbmsuQWVzR2NtS2V5EhIaEE6tD2yE5AWYOirhmkY-r3sYARABGKbvh_ILIAE"
-	t.Setenv("FTL_KMS_URI", uri)
+// WithJava is a Run* option that ensures the Java runtime is built.
+func WithJava() Option {
+	return func(o *options) {
+		o.requireJava = true
+	}
+}
 
-	run(t, ftlConfigPath, true, false, actions...)
+// WithoutController is a Run* option that disables starting the controller.
+func WithoutController() Option {
+	return func(o *options) {
+		o.startController = false
+	}
 }
 
-func run(t *testing.T, ftlConfigPath string, startController bool, requireJava bool, actions ...Action) {
+type options struct {
+	languages       []string
+	ftlConfigPath   string
+	startController bool
+	requireJava     bool
+	envars          map[string]string
+}
+
+// Run an integration test.
+func Run(t *testing.T, actionsOrOptions ...ActionOrOption) {
+	run(t, actionsOrOptions...)
+}
+
+func run(t *testing.T, actionsOrOptions ...ActionOrOption) {
+	opts := options{
+		startController: true,
+		languages:       []string{"go"},
+		envars:          map[string]string{},
+	}
+	actions := []Action{}
+	for _, opt := range actionsOrOptions {
+		switch o := opt.(type) {
+		case Action:
+			actions = append(actions, o)
+
+		case func(t testing.TB, ic TestContext):
+			actions = append(actions, Action(o))
+
+		case Option:
+			o(&opts)
+
+		case func(*options):
+			o(&opts)
+
+		default:
+			panic(fmt.Sprintf("expected Option or Action, not %T", opt))
+		}
+	}
+
+	for key, value := range opts.envars {
+		t.Setenv(key, value)
+	}
+
 	tmpDir := t.TempDir()
 
 	cwd, err := os.Getwd()
@@ -92,12 +143,13 @@ func run(t *testing.T, ftlConfigPath string, startController bool, requireJava b
 	rootDir, ok := internal.GitRoot("").Get()
 	assert.True(t, ok)
 
-	if ftlConfigPath != "" {
-		ftlConfigPath = filepath.Join(cwd, "testdata", "go", ftlConfigPath)
+	if opts.ftlConfigPath != "" {
+		// TODO: We shouldn't be copying the shared config from the "go" testdata...
+		opts.ftlConfigPath = filepath.Join(cwd, "testdata", "go", opts.ftlConfigPath)
 		projectPath := filepath.Join(tmpDir, "ftl-project.toml")
 
 		// Copy the specified FTL config to the temporary directory.
-		err = copy.Copy(ftlConfigPath, projectPath)
+		err = copy.Copy(opts.ftlConfigPath, projectPath)
 		if err == nil {
 			t.Setenv("FTL_CONFIG", projectPath)
 		} else {
@@ -106,8 +158,8 @@ func run(t *testing.T, ftlConfigPath string, startController bool, requireJava b
 			// can't be loaded until the module is copied over, and the config itself
 			// is used by FTL during startup.
 			// Some tests still rely on this behavior, so we can't remove it entirely.
-			t.Logf("Failed to copy %s to %s: %s", ftlConfigPath, projectPath, err)
-			t.Setenv("FTL_CONFIG", ftlConfigPath)
+			t.Logf("Failed to copy %s to %s: %s", opts.ftlConfigPath, projectPath, err)
+			t.Setenv("FTL_CONFIG", opts.ftlConfigPath)
 		}
 
 	} else {
@@ -124,49 +176,53 @@ func run(t *testing.T, ftlConfigPath string, startController bool, requireJava b
 		Infof("Building ftl")
 		err = ftlexec.Command(ctx, log.Debug, rootDir, "just", "build", "ftl").RunBuffered(ctx)
 		assert.NoError(t, err)
-		if requireJava {
+		if opts.requireJava {
 			err = ftlexec.Command(ctx, log.Debug, rootDir, "just", "build-java").RunBuffered(ctx)
 			assert.NoError(t, err)
 		}
 	})
 
-	verbs := rpc.Dial(ftlv1connect.NewVerbServiceClient, "http://localhost:8892", log.Debug)
-
-	var controller ftlv1connect.ControllerServiceClient
-	var console pbconsoleconnect.ConsoleServiceClient
-	if startController {
-		controller = rpc.Dial(ftlv1connect.NewControllerServiceClient, "http://localhost:8892", log.Debug)
-		console = rpc.Dial(pbconsoleconnect.NewConsoleServiceClient, "http://localhost:8892", log.Debug)
-
-		Infof("Starting ftl cluster")
-		ctx = startProcess(ctx, t, filepath.Join(binDir, "ftl"), "serve", "--recreate")
-	}
-
-	ic := TestContext{
-		Context:  ctx,
-		RootDir:  rootDir,
-		testData: filepath.Join(cwd, "testdata", "go"),
-		workDir:  tmpDir,
-		binDir:   binDir,
-		Verbs:    verbs,
-	}
-
-	if startController {
-		ic.Controller = controller
-		ic.Console = console
-
-		Infof("Waiting for controller to be ready")
-		ic.AssertWithRetry(t, func(t testing.TB, ic TestContext) {
-			_, err := ic.Controller.Status(ic, connect.NewRequest(&ftlv1.StatusRequest{}))
-			assert.NoError(t, err)
+	for _, language := range opts.languages {
+		t.Run(language, func(t *testing.T) {
+			verbs := rpc.Dial(ftlv1connect.NewVerbServiceClient, "http://localhost:8892", log.Debug)
+
+			var controller ftlv1connect.ControllerServiceClient
+			var console pbconsoleconnect.ConsoleServiceClient
+			if opts.startController {
+				controller = rpc.Dial(ftlv1connect.NewControllerServiceClient, "http://localhost:8892", log.Debug)
+				console = rpc.Dial(pbconsoleconnect.NewConsoleServiceClient, "http://localhost:8892", log.Debug)
+
+				Infof("Starting ftl cluster")
+				ctx = startProcess(ctx, t, filepath.Join(binDir, "ftl"), "serve", "--recreate")
+			}
+
+			ic := TestContext{
+				Context:  ctx,
+				RootDir:  rootDir,
+				testData: filepath.Join(cwd, "testdata", language),
+				workDir:  tmpDir,
+				binDir:   binDir,
+				Verbs:    verbs,
+			}
+
+			if opts.startController {
+				ic.Controller = controller
+				ic.Console = console
+
+				Infof("Waiting for controller to be ready")
+				ic.AssertWithRetry(t, func(t testing.TB, ic TestContext) {
+					_, err := ic.Controller.Status(ic, connect.NewRequest(&ftlv1.StatusRequest{}))
+					assert.NoError(t, err)
+				})
+			}
+
+			Infof("Starting test")
+
+			for _, action := range actions {
+				ic.AssertWithRetry(t, action)
+			}
 		})
 	}
-
-	Infof("Starting test")
-
-	for _, action := range actions {
-		ic.AssertWithRetry(t, action)
-	}
 }
 
 type TestContext struct {
@@ -249,7 +305,7 @@ func (l *logWriter) Write(p []byte) (n int, err error) {
 	}
 }
 
-// startProcess runs a binary in the background.
+// startProcess runs a binary in the background and terminates it when the test completes.
 func startProcess(ctx context.Context, t testing.TB, args ...string) context.Context {
 	t.Helper()
 	ctx, cancel := context.WithCancel(ctx)
diff --git a/internal/encryption/integration_test.go b/internal/encryption/integration_test.go
index 4b0c35d50..d56462e10 100644
--- a/internal/encryption/integration_test.go
+++ b/internal/encryption/integration_test.go
@@ -24,8 +24,13 @@ import (
 	awsv1kms "github.com/aws/aws-sdk-go/service/kms"
 )
 
+func WithEncryption() in.Option {
+	return in.WithEnvar("FTL_KMS_URI", "fake-kms://CKbvh_ILElQKSAowdHlwZS5nb29nbGVhcGlzLmNvbS9nb29nbGUuY3J5cHRvLnRpbmsuQWVzR2NtS2V5EhIaEE6tD2yE5AWYOirhmkY-r3sYARABGKbvh_ILIAE")
+}
+
 func TestEncryptionForLogs(t *testing.T) {
-	in.RunWithEncryption(t, "",
+	in.Run(t,
+		WithEncryption(),
 		in.CopyModule("encryption"),
 		in.Deploy("encryption"),
 		in.Call[map[string]interface{}, any]("encryption", "echo", map[string]interface{}{"name": "Alice"}, nil),
@@ -61,7 +66,8 @@ func TestEncryptionForLogs(t *testing.T) {
 }
 
 func TestEncryptionForPubSub(t *testing.T) {
-	in.RunWithEncryption(t, "",
+	in.Run(t,
+		WithEncryption(),
 		in.CopyModule("encryption"),
 		in.Deploy("encryption"),
 		in.Call[map[string]interface{}, any]("encryption", "publish", map[string]interface{}{"name": "AliceInWonderland"}, nil),
@@ -81,7 +87,8 @@ func TestEncryptionForPubSub(t *testing.T) {
 }
 
 func TestEncryptionForFSM(t *testing.T) {
-	in.RunWithEncryption(t, "",
+	in.Run(t,
+		WithEncryption(),
 		in.CopyModule("encryption"),
 		in.Deploy("encryption"),
 		in.Call[map[string]interface{}, any]("encryption", "beginFsm", map[string]interface{}{"name": "Rosebud"}, nil),
diff --git a/java-runtime/java_integration_test.go b/java-runtime/java_integration_test.go
index d64f14854..0680b4989 100644
--- a/java-runtime/java_integration_test.go
+++ b/java-runtime/java_integration_test.go
@@ -14,7 +14,8 @@ import (
 )
 
 func TestJavaToGoCall(t *testing.T) {
-	in.RunWithJava(t, "",
+	in.Run(t,
+		in.WithJava(),
 		in.CopyModule("gomodule"),
 		in.CopyDir("javamodule", "javamodule"),
 		in.Deploy("gomodule"),