diff --git a/gopls/internal/regtest/diagnostics_test.go b/gopls/internal/regtest/diagnostics_test.go
index d9450c0..109561a 100644
--- a/gopls/internal/regtest/diagnostics_test.go
+++ b/gopls/internal/regtest/diagnostics_test.go
@@ -282,9 +282,9 @@
 	})
 
 	t.Run("without workspace module", func(t *testing.T) {
-		withOptions(EditorConfig{
-			WithoutExperimentalWorkspaceModule: true,
-		}).run(t, noMod, func(t *testing.T, env *Env) {
+		withOptions(
+			WithModes(WithoutExperiments),
+		).run(t, noMod, func(t *testing.T, env *Env) {
 			env.Await(
 				env.DiagnosticAtRegexp("main.go", `"mod.com/bob"`),
 			)
diff --git a/gopls/internal/regtest/modfile_test.go b/gopls/internal/regtest/modfile_test.go
index 71e8729..49469bf 100644
--- a/gopls/internal/regtest/modfile_test.go
+++ b/gopls/internal/regtest/modfile_test.go
@@ -587,9 +587,9 @@
 			Env: map[string]string{
 				"GOFLAGS": "-mod=readonly",
 			},
-			WithoutExperimentalWorkspaceModule: true,
 		},
 		WithProxyFiles(proxy),
+		WithModes(WithoutExperiments),
 	).run(t, mod, func(t *testing.T, env *Env) {
 		env.OpenFile("main.go")
 		original := env.ReadWorkspaceFile("go.mod")
@@ -639,6 +639,7 @@
 `
 	withOptions(
 		WithProxyFiles(workspaceProxy),
+		WithModes(Experimental),
 	).run(t, mod, func(t *testing.T, env *Env) {
 		env.Await(
 			env.DiagnosticAtRegexp("a/go.mod", "example.com v1.2.3"),
diff --git a/gopls/internal/regtest/runner.go b/gopls/internal/regtest/runner.go
index feffdc4..9f8a779 100644
--- a/gopls/internal/regtest/runner.go
+++ b/gopls/internal/regtest/runner.go
@@ -28,6 +28,7 @@
 	"golang.org/x/tools/internal/lsp/fake"
 	"golang.org/x/tools/internal/lsp/lsprpc"
 	"golang.org/x/tools/internal/lsp/protocol"
+	"golang.org/x/tools/internal/lsp/source"
 )
 
 // Mode is a bitmask that defines for which execution modes a test should run.
@@ -43,9 +44,16 @@
 	Forwarded
 	// SeparateProcess forwards connection to a shared separate gopls process.
 	SeparateProcess
+	// Experimental enables all of the experimental configurations that are
+	// being developed. Currently, it enables the workspace module.
+	Experimental
+	// WithoutExperiments are the modes that run without experimental features,
+	// like the workspace module. These should be used for tests that only work
+	// in the default modes.
+	WithoutExperiments = Singleton | Forwarded
 	// NormalModes are the global default execution modes, when unmodified by
 	// test flags or by individual test options.
-	NormalModes = Singleton
+	NormalModes = Singleton | Experimental
 )
 
 // A Runner runs tests in gopls execution environments, as specified by its
@@ -218,6 +226,7 @@
 		{"singleton", Singleton, singletonServer},
 		{"forwarded", Forwarded, r.forwardedServer},
 		{"separate_process", SeparateProcess, r.separateProcessServer},
+		{"experimental_workspace_module", Experimental, experimentalWorkspaceModule},
 	}
 
 	for _, tc := range tests {
@@ -333,6 +342,14 @@
 	return lsprpc.NewStreamServer(cache.New(ctx, hooks.Options), false)
 }
 
+func experimentalWorkspaceModule(ctx context.Context, t *testing.T) jsonrpc2.StreamServer {
+	options := func(o *source.Options) {
+		hooks.Options(o)
+		o.ExperimentalWorkspaceModule = true
+	}
+	return lsprpc.NewStreamServer(cache.New(ctx, options), false)
+}
+
 func (r *Runner) forwardedServer(ctx context.Context, t *testing.T) jsonrpc2.StreamServer {
 	ts := r.getTestServer()
 	return lsprpc.NewForwarder("tcp", ts.Addr)
diff --git a/gopls/internal/regtest/vendor_test.go b/gopls/internal/regtest/vendor_test.go
index b34ac33..7f11d4a 100644
--- a/gopls/internal/regtest/vendor_test.go
+++ b/gopls/internal/regtest/vendor_test.go
@@ -40,9 +40,7 @@
 `
 	// TODO(rstambler): Remove this when golang/go#41819 is resolved.
 	withOptions(
-		EditorConfig{
-			WithoutExperimentalWorkspaceModule: true,
-		},
+		WithModes(WithoutExperiments),
 		WithProxyFiles(basicProxy),
 	).run(t, pkgThatUsesVendoring, func(t *testing.T, env *Env) {
 		env.OpenFile("a/a1.go")
diff --git a/gopls/internal/regtest/workspace_test.go b/gopls/internal/regtest/workspace_test.go
index 5a4c029..35027e8 100644
--- a/gopls/internal/regtest/workspace_test.go
+++ b/gopls/internal/regtest/workspace_test.go
@@ -121,38 +121,6 @@
 	}
 }
 
-// Tests that basic functionality works without ExperimentalWorkspaceModule.
-func TestNoWorkspaceModule(t *testing.T) {
-	const mod = `
--- go.mod --
-module mod.com
-
-go 1.14
--- main.go --
-package main
-
-import "mod.com/pkg/inner"
-
-func main() {
-	inner.Hi()
-}
--- pkg/inner/inner.go --
-package inner
-
-func Hi() {}
-`
-	withOptions(
-		EditorConfig{
-			WithoutExperimentalWorkspaceModule: true,
-		},
-	).run(t, mod, func(t *testing.T, env *Env) {
-		env.OpenFile("main.go")
-		env.Await(
-			NoDiagnostics("main.go"),
-		)
-	})
-}
-
 // Make sure that analysis diagnostics are cleared for the whole package when
 // the only opened file is closed. This test was inspired by the experience in
 // VS Code, where clicking on a reference result triggers a
@@ -230,6 +198,7 @@
 `
 	withOptions(
 		WithProxyFiles(workspaceModuleProxy),
+		WithModes(Experimental),
 	).run(t, multiModule, func(t *testing.T, env *Env) {
 		env.Await(
 			env.DiagnosticAtRegexp("moda/a/a.go", "x"),
@@ -271,6 +240,7 @@
 `
 	withOptions(
 		WithProxyFiles(workspaceModuleProxy),
+		WithModes(Experimental),
 	).run(t, multiModule, func(t *testing.T, env *Env) {
 		env.OpenFile("moda/a/a.go")
 
@@ -313,6 +283,7 @@
 }
 `
 	withOptions(
+		WithModes(Experimental),
 		WithProxyFiles(workspaceModuleProxy),
 	).run(t, multiModule, func(t *testing.T, env *Env) {
 		env.OpenFile("moda/a/a.go")
@@ -375,6 +346,7 @@
 `
 	withOptions(
 		WithProxyFiles(workspaceModuleProxy),
+		WithModes(Experimental),
 	).run(t, multiModule, func(t *testing.T, env *Env) {
 		env.OpenFile("modb/go.mod")
 		env.Await(
@@ -430,6 +402,7 @@
 `
 	withOptions(
 		WithProxyFiles(workspaceModuleProxy),
+		WithModes(Experimental),
 	).run(t, multiModule, func(t *testing.T, env *Env) {
 		env.OpenFile("moda/a/a.go")
 		original, _ := env.GoToDefinition("moda/a/a.go", env.RegexpSearch("moda/a/a.go", "Hello"))
diff --git a/internal/lsp/fake/editor.go b/internal/lsp/fake/editor.go
index f983062..5e977a4 100644
--- a/internal/lsp/fake/editor.go
+++ b/internal/lsp/fake/editor.go
@@ -85,12 +85,6 @@
 	// EnableStaticcheck enables staticcheck analyzers.
 	EnableStaticcheck bool
 
-	// WithoutExperimentalWorkspaceModule disables the experimental workspace
-	// module.
-	// TODO(rstambler): This mode is temporary and should be removed when
-	// golang.org/cl/258518 is merged.
-	WithoutExperimentalWorkspaceModule bool
-
 	// AllExperiments sets the "allExperiments" configuration, which enables
 	// all of gopls's opt-in settings.
 	AllExperiments bool
@@ -203,12 +197,6 @@
 	if e.Config.EnableStaticcheck {
 		config["staticcheck"] = true
 	}
-	// Default to using the experimental workspace module mode, unless
-	// explicitly configured.
-	if !e.Config.WithoutExperimentalWorkspaceModule {
-		config["experimentalWorkspaceModule"] = true
-	}
-
 	if e.Config.AllExperiments {
 		config["allExperiments"] = true
 	}
@@ -217,6 +205,7 @@
 	// default... and probably change to the new settings name.
 	// config["experimentalDiagnosticsDelay"] = "10ms"
 
+	// ExperimentalWorkspaceModule is only set as a mode, not a configuration.
 	return config
 }