chore: migrate deploy_test to integration tests in buildengine (#2505)

This tests the same things as the old test, but through slightly higher
abstraction layer (cli instead of calling build engine functions
directly)

The same functions as in the original test should get called via the cli
in the integration test.

See #1585

internal/buildengine/deploy_integration_test.go

@@ -0,0 +1,23 @@
+//go:build integration
+
+package buildengine
+
+import (
+	"testing"
+
+	in "github.com/TBD54566975/ftl/internal/integration"
+)
+
+func TestDeploy(t *testing.T) {
+	in.Run(t,
+		in.WithTestDataDir("testdata"),
+		in.CopyModule("another"),
+
+		// Build first to make sure the files are there.
+		in.Build("another"),
+		in.FileExists("/another/.ftl/main"),
+
+		// Test that the deployment works and starts correctly
+		in.Deploy("another"),
+	)
+}

internal/integration/harness.go

@@ -59,6 +59,15 @@ func WithLanguages(languages ...string) Option {
 	}
 }
 
+// WithTestDataDir sets the directory from which to look for test data.
+//
+// Defaults to "testdata/<language>" if not provided.
+func WithTestDataDir(dir string) Option {
+	return func(o *options) {
+		o.testDataDir = dir
+	}
+}
+
 // WithFTLConfig is a Run* option that specifies the FTL config to use.
 //
 // This will set FTL_CONFIG for this test, then pass in the relative
@@ -97,6 +106,7 @@ func WithoutController() Option {
 
 type options struct {
 	languages       []string
+	testDataDir     string
 	ftlConfigPath   string
 	startController bool
 	requireJava     bool
@@ -176,10 +186,15 @@ func run(t *testing.T, actionsOrOptions ...ActionOrOption) {
 				ctx = startProcess(ctx, t, filepath.Join(binDir, "ftl"), "serve", "--recreate")
 			}
 
+			testData := filepath.Join(cwd, "testdata", language)
+			if opts.testDataDir != "" {
+				testData = opts.testDataDir
+			}
+
 			ic := TestContext{
 				Context:  ctx,
 				RootDir:  rootDir,
-				testData: filepath.Join(cwd, "testdata", language),
+				testData: testData,
 				workDir:  tmpDir,
 				binDir:   binDir,
 				Verbs:    verbs,