diff --git a/src/main/groovy/com/lesfurets/jenkins/unit/BasePipelineTest.groovy b/src/main/groovy/com/lesfurets/jenkins/unit/BasePipelineTest.groovy
index 18f8d334..efcfd9c4 100644
--- a/src/main/groovy/com/lesfurets/jenkins/unit/BasePipelineTest.groovy
+++ b/src/main/groovy/com/lesfurets/jenkins/unit/BasePipelineTest.groovy
@@ -429,40 +429,38 @@ abstract class BasePipelineTest {
         assertCallStack().contains(text)
     }
 
-
     /**
      * Helper for adding a params value in tests
      */
     void addParam(String name, Object val, Boolean overWrite = false) {
-        Map params = binding.getVariable('params') as Map
-        if (params == null) {
-            params = [:]
-            binding.setVariable('params', params)
+        if (!binding.hasVariable('params')) {
+            binding.setVariable('params', [:])
         }
+
+        Map params = binding.getVariable('params') as Map
         if (params[name] == null || overWrite) {
             params[name] = val
         }
     }
 
-
     /**
      * Helper for adding a environment value in tests
      */
     void addEnvVar(String name, String val) {
-        Map env = binding.getVariable('env') as Map
-        if (env == null) {
-            env = [:]
-            binding.setVariable('env', env)
+        if (!binding.hasVariable('env')) {
+            binding.setVariable('env', [:])
         }
+
+        Map env = binding.getVariable('env') as Map
         env[name] = val
     }
 
     void addCredential(String key, String val) {
-        Map credentials = binding.getVariable('credentials') as Map
-        if (credentials == null) {
-            credentials = [:]
-            binding.setVariable('credentials', credentials)
+        if (!binding.hasVariable('credentials')) {
+            binding.setVariable('credentials', [:])
         }
+
+        Map credentials = binding.getVariable('credentials') as Map
         credentials[key] = val
     }
 }
diff --git a/src/main/groovy/com/lesfurets/jenkins/unit/declarative/DeclarativePipelineTest.groovy b/src/main/groovy/com/lesfurets/jenkins/unit/declarative/DeclarativePipelineTest.groovy
index 6d76c993..73523805 100644
--- a/src/main/groovy/com/lesfurets/jenkins/unit/declarative/DeclarativePipelineTest.groovy
+++ b/src/main/groovy/com/lesfurets/jenkins/unit/declarative/DeclarativePipelineTest.groovy
@@ -18,11 +18,11 @@ abstract class DeclarativePipelineTest extends BasePipelineTest {
 
     def stringInterceptor = { Map desc->
         if (desc) {
-            // we are in context of paremetes { string(...)}
+            // we are in context of parameters { string(...)}
             if (desc.name) {
                 addParam(desc.name, desc.defaultValue, false)
             }
-            // we are in context of withCredentaials([string()..]) { }
+            // we are in context of withCredentials([string()..]) { }
             if(desc.variable) {
                 return desc.variable
             }
diff --git a/src/test/groovy/com/lesfurets/jenkins/TestAddCredential.groovy b/src/test/groovy/com/lesfurets/jenkins/TestAddCredential.groovy
new file mode 100644
index 00000000..54443d1a
--- /dev/null
+++ b/src/test/groovy/com/lesfurets/jenkins/TestAddCredential.groovy
@@ -0,0 +1,13 @@
+package com.lesfurets.jenkins
+
+import com.lesfurets.jenkins.unit.BasePipelineTest
+import org.junit.Test
+
+class TestAddCredential extends BasePipelineTest {
+
+    @Test
+    void readUndefinedParamNoException() throws Exception {
+        super.setUp()
+        addCredential('FOO', 'BAR')
+    }
+}
diff --git a/src/test/groovy/com/lesfurets/jenkins/TestAddEnvVar.groovy b/src/test/groovy/com/lesfurets/jenkins/TestAddEnvVar.groovy
new file mode 100644
index 00000000..d6e13bb1
--- /dev/null
+++ b/src/test/groovy/com/lesfurets/jenkins/TestAddEnvVar.groovy
@@ -0,0 +1,13 @@
+package com.lesfurets.jenkins
+
+import com.lesfurets.jenkins.unit.BasePipelineTest
+import org.junit.Test
+
+class TestAddEnvVar extends BasePipelineTest {
+
+    @Test
+    void readUndefinedParamNoException() throws Exception {
+        super.setUp()
+        addEnvVar('FOO', 'BAR')
+    }
+}
diff --git a/src/test/groovy/com/lesfurets/jenkins/TestAddParam.groovy b/src/test/groovy/com/lesfurets/jenkins/TestAddParam.groovy
new file mode 100644
index 00000000..349d7b18
--- /dev/null
+++ b/src/test/groovy/com/lesfurets/jenkins/TestAddParam.groovy
@@ -0,0 +1,13 @@
+package com.lesfurets.jenkins
+
+import com.lesfurets.jenkins.unit.BasePipelineTest
+import org.junit.Test
+
+class TestAddParam extends BasePipelineTest {
+
+    @Test
+    void readUndefinedParamNoException() throws Exception {
+        super.setUp()
+        addParam('FOO', 'BAR')
+    }
+}