diff --git a/gopls/internal/test/integration/misc/link_test.go b/gopls/internal/test/integration/misc/link_test.go
index 533b1186c61..53b0f0818f3 100644
--- a/gopls/internal/test/integration/misc/link_test.go
+++ b/gopls/internal/test/integration/misc/link_test.go
@@ -19,9 +19,6 @@ module mod.test
 go 1.12
 
 require import.test v1.2.3
--- go.sum --
-import.test v1.2.3 h1:Mu4N9BICLJFxwwn8YNg6T3frkFWW1O7evXvo0HiRjBc=
-import.test v1.2.3/go.mod h1:KooCN1g237upRg7irU7F+3oADn5tVClU8YYW4I1xhMk=
 -- main.go --
 package main
 
@@ -45,6 +42,7 @@ const Hello = "Hello"
 `
 	WithOptions(
 		ProxyFiles(proxy),
+		WriteGoSum("."),
 	).Run(t, program, func(t *testing.T, env *Env) {
 		env.OpenFile("main.go")
 		env.OpenFile("go.mod")
diff --git a/gopls/internal/test/integration/options.go b/gopls/internal/test/integration/options.go
index b36ebc9c3f8..baa13d06ecd 100644
--- a/gopls/internal/test/integration/options.go
+++ b/gopls/internal/test/integration/options.go
@@ -14,6 +14,7 @@ type runConfig struct {
 	sandbox       fake.SandboxConfig
 	modes         Mode
 	noLogsOnError bool
+	writeGoSum    []string
 }
 
 func defaultConfig() runConfig {
@@ -46,6 +47,17 @@ func ProxyFiles(txt string) RunOption {
 	})
 }
 
+// WriteGoSum causes the environment to write a go.sum file for the requested
+// relative directories (via `go list -mod=mod`), before starting gopls.
+//
+// Useful for tests that use ProxyFiles, but don't care about crafting the
+// go.sum content.
+func WriteGoSum(dirs ...string) RunOption {
+	return optionSetter(func(opts *runConfig) {
+		opts.writeGoSum = dirs
+	})
+}
+
 // Modes configures the execution modes that the test should run in.
 //
 // By default, modes are configured by the test runner. If this option is set,
diff --git a/gopls/internal/test/integration/runner.go b/gopls/internal/test/integration/runner.go
index ed333585ddf..adb307f1901 100644
--- a/gopls/internal/test/integration/runner.go
+++ b/gopls/internal/test/integration/runner.go
@@ -210,6 +210,13 @@ func (r *Runner) Run(t *testing.T, files string, test TestFunc, opts ...RunOptio
 				}
 			}()
 
+			// Write the go.sum file for the requested directories, before starting the server.
+			for _, dir := range config.writeGoSum {
+				if err := sandbox.RunGoCommand(context.Background(), dir, "list", []string{"-mod=mod", "./..."}, []string{"GOWORK=off"}, true); err != nil {
+					t.Fatal(err)
+				}
+			}
+
 			ss := tc.getServer(r.OptionsHook)
 
 			framer := jsonrpc2.NewRawStream
diff --git a/gopls/internal/test/integration/wrappers.go b/gopls/internal/test/integration/wrappers.go
index cc4a66d79fd..ce51208d0a3 100644
--- a/gopls/internal/test/integration/wrappers.go
+++ b/gopls/internal/test/integration/wrappers.go
@@ -318,10 +318,10 @@ func (e *Env) GoVersion() int {
 func (e *Env) DumpGoSum(dir string) {
 	e.T.Helper()
 
-	if err := e.Sandbox.RunGoCommand(e.Ctx, dir, "list", []string{"-mod=mod", "..."}, nil, true); err != nil {
+	if err := e.Sandbox.RunGoCommand(e.Ctx, dir, "list", []string{"-mod=mod", "./..."}, nil, true); err != nil {
 		e.T.Fatal(err)
 	}
-	sumFile := path.Join(dir, "/go.sum")
+	sumFile := path.Join(dir, "go.sum")
 	e.T.Log("\n\n-- " + sumFile + " --\n" + e.ReadWorkspaceFile(sumFile))
 	e.T.Fatal("see contents above")
 }