diff --git a/assertions/directoryExist.ts b/assertions/directoryExist.ts
new file mode 100644
index 00000000..8ef7c335
--- /dev/null
+++ b/assertions/directoryExist.ts
@@ -0,0 +1,10 @@
+import { RunResult } from "../engine/run_result";
+import * as fs from "fs";
+
+export class DirectoryExist {
+    public static run(directory: string): void {
+        if(!fs.existsSync(directory)) {
+            throw new Error("directory " + directory + " does not exist");
+        }
+    }
+}
\ No newline at end of file
diff --git a/assertions/index.ts b/assertions/index.ts
index 402eed45..6946937c 100644
--- a/assertions/index.ts
+++ b/assertions/index.ts
@@ -3,9 +3,10 @@ import { Step } from "../engine/step";
 import { Command } from "../engine/command";
 import { NoErrorCode } from "./noErrorCode";
 import { NoException } from "./noException";
+import { DirectoryExist } from "./directoryExist";
 
 
-export class Assertions{
+export class Assertions {
 
     public noErrorCode(result: RunResult): Assertions {
         NoErrorCode.run(result);
@@ -16,4 +17,9 @@ export class Assertions{
         NoException.run(result);
         return this;
     }
+
+    public directoryExits(directory: string): Assertions {
+        DirectoryExist.run(directory);
+        return this;
+    }
 }
\ No newline at end of file
diff --git a/assertions/noErrorCode.ts b/assertions/noErrorCode.ts
index c87183ce..95e8ef1e 100644
--- a/assertions/noErrorCode.ts
+++ b/assertions/noErrorCode.ts
@@ -1,8 +1,8 @@
 import { RunResult } from "../engine/run_result";
 
-export class NoErrorCode{
+export class NoErrorCode {
     public static run(result: RunResult): void {
-        if(result.returnCode != 0){
+        if(result.returnCode != 0) {
             throw new Error("returnCode is not 0");
         }
     }
diff --git a/assertions/noException.ts b/assertions/noException.ts
index 17cdc193..f2ae777b 100644
--- a/assertions/noException.ts
+++ b/assertions/noException.ts
@@ -2,7 +2,7 @@ import { RunResult } from "../engine/run_result";
 
 export class NoException {
     public static run(result: RunResult): void {
-        if(result.exceptions.length > 0){
+        if(result.exceptions.length > 0) {
             throw new Error("Unexpected exception.");
         }
     }