diff --git a/spec/mock_jasmine.ts b/spec/mock_jasmine.ts
index 61bae1f503b01a63743515782823e7b9f1dceefb..17bffedd0e0a95929b3cb34f6d732c3d3cc8a31e 100644
--- a/spec/mock_jasmine.ts
+++ b/spec/mock_jasmine.ts
@@ -92,9 +92,13 @@ class Expect {
      * Mock de la fonction toBeTruthy de Jasmine : the actual value should be true
      * @param message message d'erreur
      */
-    public toBeTruthy(message: string) {
+    public toBeTruthy(message?: string) {
         if (!this.actual) {
-            console.error(message);
+            if (message !== undefined) {
+                console.error(message);
+            } else {
+                console.error(`${this.actual} should be true`);
+            }
         }
     }
 
@@ -102,23 +106,27 @@ class Expect {
      * Mock de la fonction toBeFalsy de Jasmine : the actual value should be false
      * @param message message d'erreur
      */
-    public toBeFalsy(message: string) {
+    public toBeFalsy(message?: string) {
         if (this.actual) {
-            console.error(message);
+            if (message !== undefined) {
+                console.error(message);
+            } else {
+                console.error(`${this.actual} should be false`);
+            }
         }
     }
 
     public toBeUndefined(message?: string) {
         if (this.actual !== undefined) {
-            if (message === undefined) {
+            if (message !== undefined) {
                 console.error(message);
             } else {
-                console.error(this.actual + " should be undefined");
+                console.error(`${this.actual} should be undefined`);
             }
         }
     }
 
-    public toThrow(expected: any) {
+    public toThrow(expected?: any) {
         let exception: Error;
         if (typeof this.actual !== "function") {
             throw new Error("Actual is not a function");
@@ -128,11 +136,16 @@ class Expect {
         } catch (e) {
             exception = e;
         }
-        if (exception) {
-            if (exception === undefined) {
-                console.error("Expected tested function to thow an error");
-            } else if (exception.message !== expected.message) {
-                console.error("Function throws " + exception.message + " and " + expected.message + " was expected");
+        if (exception === undefined) {
+            console.error("Expected tested function to throw an error");
+        } else {
+            if (expected) {
+                if (exception.message !== expected.message) {
+                    console.error(`Function throws '${exception.message}' but '${expected.message}' was expected`);
+                }
+            }
+            else if (exception.message) {
+                console.error(`Function throws '${exception.message}' but no message was expected`);
             }
         }
     }