diff --git a/src/cmd_line/main.ts b/src/cmd_line/main.ts
index 22db132ea..289e040b3 100644
--- a/src/cmd_line/main.ts
+++ b/src/cmd_line/main.ts
@@ -23,7 +23,7 @@ export async function showCmdLine(initialText: string, modeHandler : ModeHandler
     }
 }
 
-function runCmdLine(command : string, modeHandler : ModeHandler) : Promise<{}> {
+export async function runCmdLine(command : string, modeHandler : ModeHandler) : Promise<{}> {
     if (!command || command.length === 0) {
         return;
     }
@@ -34,7 +34,7 @@ function runCmdLine(command : string, modeHandler : ModeHandler) : Promise<{}> {
             return;
         }
 
-        cmd.execute(vscode.window.activeTextEditor, modeHandler);
+        await cmd.execute(vscode.window.activeTextEditor, modeHandler);
     } catch (e) {
         modeHandler.setupStatusBarItem(e.toString());
     }
diff --git a/src/cmd_line/node.ts b/src/cmd_line/node.ts
index f661cf9c0..9fe0db8f7 100644
--- a/src/cmd_line/node.ts
+++ b/src/cmd_line/node.ts
@@ -87,16 +87,16 @@ export class CommandLine {
         return ":" + this.range.toString() + " " + this.command.toString();
     }
 
-    execute(document : vscode.TextEditor, modeHandler : ModeHandler) : void {
+    async execute(document : vscode.TextEditor, modeHandler : ModeHandler) : Promise<void> {
         if (!this.command) {
             this.range.execute(document);
             return;
         }
 
         if (this.range.isEmpty) {
-            this.command.execute(modeHandler);
+            await this.command.execute(modeHandler);
         } else {
-            this.command.executeWithRange(modeHandler, this.range);
+            await this.command.executeWithRange(modeHandler, this.range);
         }
 
     }
diff --git a/test/cmd_line/substitute.test.ts b/test/cmd_line/substitute.test.ts
new file mode 100644
index 000000000..ee97aeb1a
--- /dev/null
+++ b/test/cmd_line/substitute.test.ts
@@ -0,0 +1,59 @@
+"use strict";
+
+import * as assert from 'assert';
+import { ModeHandler } from '../../src/mode/modeHandler';
+import { setupWorkspace, cleanUpWorkspace, assertEqualLines, assertEqual } from './../testUtils';
+import { ModeName } from '../../src/mode/mode';
+import { TextEditor } from '../../src/textEditor';
+import { runCmdLine } from '../../src/cmd_line/main';
+
+suite("Basic substitute", () => {
+    let modeHandler: ModeHandler;
+
+    setup(async () => {
+        await setupWorkspace();
+        modeHandler = new ModeHandler();
+    });
+
+    teardown(cleanUpWorkspace);
+
+    test("Replace single word once", async () => {
+        await modeHandler.handleMultipleKeyEvents(['i', 'a', 'b', 'a', '<esc>']);
+        await runCmdLine("%s/a/d", modeHandler);
+
+        assertEqualLines([
+            "dba"
+        ]);
+    });
+
+    test("Replace with `g` flag", async () => {
+        await modeHandler.handleMultipleKeyEvents(['i', 'a', 'b', 'a', '<esc>']);
+        await runCmdLine("%s/a/d/g", modeHandler);
+
+        assertEqualLines([
+            "dbd"
+        ]);
+    });
+
+    test("Replace multiple lines", async () => {
+        await modeHandler.handleMultipleKeyEvents(['i', 'a', 'b', 'a', '<esc>', 'o', 'a', 'b']);
+        await runCmdLine("%s/a/d/g", modeHandler);
+
+        assertEqualLines([
+            "dbd",
+            "db"
+        ]);
+    });
+
+    test("Replace across specific lines", async () => {
+        await modeHandler.handleMultipleKeyEvents(['i', 'a', 'b', 'a', '<esc>', 'o', 'a', 'b']);
+        await runCmdLine("1,1s/a/d/g", modeHandler);
+
+        assertEqualLines([
+            "dbd",
+            "ab"
+        ]);
+    });
+
+
+});
\ No newline at end of file