diff --git a/src/main/java/fr/nancy/iut/CalcEngine.java b/src/main/java/fr/nancy/iut/CalcEngine.java
index d8c58f8fe00183a559833473f2d37e7e5af525ad..7a8b3f6001a54d009fcf46e5e2f46e93d6ad9e61 100755
--- a/src/main/java/fr/nancy/iut/CalcEngine.java
+++ b/src/main/java/fr/nancy/iut/CalcEngine.java
@@ -82,10 +82,11 @@ public class CalcEngine
         if (previousOperator == '+') {
             displayValue = leftOperand + displayValue;
         }
-        else {
+        else if(previousOperator == '-'){
             displayValue = leftOperand - displayValue;
         }
         leftOperand = 0;
+        this.previousOperator = ' ';
     }
 
     /**
diff --git a/src/test/java/fr/nancy/iut/CalcEngineTest.java b/src/test/java/fr/nancy/iut/CalcEngineTest.java
index aff861bada62f93d35cdddcf5965b022920a91c0..7dbf820687863d0db68bcfc03847ac19ac7a6796 100644
--- a/src/test/java/fr/nancy/iut/CalcEngineTest.java
+++ b/src/test/java/fr/nancy/iut/CalcEngineTest.java
@@ -5,12 +5,11 @@ import org.junit.jupiter.api.Test;
 
 import static org.junit.jupiter.api.Assertions.assertEquals;
 
-public class CalcEngineTest  {
-    
+public class CalcEngineTest {
+
 
     @Test
-    public void testClear()
-    {
+    public void testClear() {
         CalcEngine calcEngine = new CalcEngine();
         calcEngine.numberPressed(350);
         calcEngine.clear();
@@ -18,8 +17,7 @@ public class CalcEngineTest  {
     }
 
     @Test
-    public void testEquals()
-    {
+    public void testEquals() {
         CalcEngine calcEngine = new CalcEngine();
         calcEngine.numberPressed(5);
         calcEngine.plus();
@@ -30,15 +28,13 @@ public class CalcEngineTest  {
     }
 
     @Test
-    public void testGetAuthor()
-    {
+    public void testGetAuthor() {
         CalcEngine calcEngine = new CalcEngine();
         assertEquals("Hacker T. Largebrain", calcEngine.getAuthor());
     }
 
     @Test
-    public void testGetDisplayValue()
-    {
+    public void testGetDisplayValue() {
         CalcEngine calcEngine = new CalcEngine();
         calcEngine.numberPressed(25);
         assertEquals(25, calcEngine.getDisplayValue());
@@ -48,22 +44,19 @@ public class CalcEngineTest  {
     }
 
     @Test
-    public void testGetTitle()
-    {
+    public void testGetTitle() {
         CalcEngine calcEngine = new CalcEngine();
         assertEquals("Super Calculator", calcEngine.getTitle());
     }
 
     @Test
-    public void testGetVersion()
-    {
+    public void testGetVersion() {
         CalcEngine calcEngine = new CalcEngine();
         assertEquals("version 0.2", calcEngine.getVersion());
     }
 
     @Test
-    public void testMinus()
-    {
+    public void testMinus() {
         CalcEngine calcEngine = new CalcEngine();
         calcEngine.numberPressed(15);
         calcEngine.minus();
@@ -74,8 +67,7 @@ public class CalcEngineTest  {
     }
 
     @Test
-    public void testNumberPressed()
-    {
+    public void testNumberPressed() {
         CalcEngine calcEngine = new CalcEngine();
         calcEngine.numberPressed(12);
         assertEquals(12, calcEngine.getDisplayValue());
@@ -85,8 +77,7 @@ public class CalcEngineTest  {
     }
 
     @Test
-    public void testPlus()
-    {
+    public void testPlus() {
         CalcEngine calcEngine = new CalcEngine();
         calcEngine.numberPressed(10);
         calcEngine.plus();
@@ -97,8 +88,7 @@ public class CalcEngineTest  {
     }
 
     @Test
-    public void testPlusPuisMinus()
-    {
+    public void testPlusPuisMinus() {
         CalcEngine calcEngine = new CalcEngine();
         calcEngine.numberPressed(10);
         calcEngine.plus();
@@ -111,8 +101,7 @@ public class CalcEngineTest  {
     }
 
     @Test
-    public void testMinusPuisPlus()
-    {
+    public void testMinusPuisPlus() {
         CalcEngine calcEngine = new CalcEngine();
         calcEngine.numberPressed(10);
         calcEngine.minus();
@@ -124,4 +113,30 @@ public class CalcEngineTest  {
         assertEquals(7, calcEngine.getDisplayValue());
     }
 
+
+    /**
+     * Pour régler l'erreur trigger ci-dessus il faut rajouter la ligne "this.previousOperator = ' ';" à la
+     * fin de la méthode equals()
+     */
+    @Test
+    public void testTriggerErreur() {
+        CalcEngine calcEngine = new CalcEngine();
+        calcEngine.numberPressed(10);
+        calcEngine.plus();
+        calcEngine.numberPressed(50);
+        calcEngine.plus();
+        calcEngine.numberPressed(12);
+        calcEngine.equals();
+        calcEngine.minus();
+        calcEngine.numberPressed(20);
+        calcEngine.equals();
+        calcEngine.minus();
+        calcEngine.numberPressed(30);
+        calcEngine.minus();
+        calcEngine.numberPressed(5);
+
+        calcEngine.equals();
+        assertEquals(17, calcEngine.getDisplayValue());
+    }
+
 }