diff --git a/typescript-generator-core/src/test/java/cz/habarta/typescript/generator/Jackson2DeserializableRootType.java b/typescript-generator-core/src/test/java/cz/habarta/typescript/generator/Jackson2DeserializableRootType.java
index 6523949ae..b4a71d3e5 100644
--- a/typescript-generator-core/src/test/java/cz/habarta/typescript/generator/Jackson2DeserializableRootType.java
+++ b/typescript-generator-core/src/test/java/cz/habarta/typescript/generator/Jackson2DeserializableRootType.java
@@ -1,7 +1,6 @@
 
 package cz.habarta.typescript.generator;
 
-import static org.junit.Assert.assertSame;
 import com.fasterxml.jackson.annotation.JsonSubTypes;
 import com.fasterxml.jackson.annotation.JsonTypeInfo;
 import com.fasterxml.jackson.annotation.JsonTypeName;
@@ -24,8 +23,8 @@ public void testHowJacksonDeserializes() throws JsonProcessingException {
                         .readValue("{\"type\": \"subType\"}",
                                         NonAbstractRoot.class);
 
-        assertSame(NonAbstractRoot.class, nar.getClass());
-        assertSame(NonAbstractRootSub.class, nars.getClass());
+        Assert.assertSame(NonAbstractRoot.class, nar.getClass());
+        Assert.assertSame(NonAbstractRootSub.class, nars.getClass());
     }
 
     @Test
diff --git a/typescript-generator-core/src/test/java/cz/habarta/typescript/generator/JsonDeserializationTest.java b/typescript-generator-core/src/test/java/cz/habarta/typescript/generator/JsonDeserializationTest.java
index 7614900c0..134683dfb 100644
--- a/typescript-generator-core/src/test/java/cz/habarta/typescript/generator/JsonDeserializationTest.java
+++ b/typescript-generator-core/src/test/java/cz/habarta/typescript/generator/JsonDeserializationTest.java
@@ -148,7 +148,7 @@ public static class Order {
         @JsonSubTypes.Type(Rectangle.class),
         @JsonSubTypes.Type(Circle.class),
     })
-    private static class Shape {
+    private abstract static class Shape {
         public ShapeMetadata metadata;
     }
 
diff --git a/typescript-generator-core/src/test/java/cz/habarta/typescript/generator/TaggedUnionsTest.java b/typescript-generator-core/src/test/java/cz/habarta/typescript/generator/TaggedUnionsTest.java
index 7cbce8671..25bcc80fa 100644
--- a/typescript-generator-core/src/test/java/cz/habarta/typescript/generator/TaggedUnionsTest.java
+++ b/typescript-generator-core/src/test/java/cz/habarta/typescript/generator/TaggedUnionsTest.java
@@ -23,7 +23,7 @@ private static class Geometry {
         @JsonSubTypes.Type(Rectangle.class),
         @JsonSubTypes.Type(Circle.class),
     })
-    private static class Shape {
+    private abstract static class Shape {
     }
 
     @JsonTypeName("square")
@@ -127,7 +127,7 @@ private static interface DiamondC extends DiamondB1, DiamondB2 {
         @JsonSubTypes.Type(DieselCar.class),
         @JsonSubTypes.Type(ElectricCar.class),
     })
-    private static class Car {
+    private abstract static class Car {
         public String name;
     }
 
diff --git a/typescript-generator-core/src/test/java/cz/habarta/typescript/generator/ext/OnePossiblePropertyValueAssigningExtensionTest.java b/typescript-generator-core/src/test/java/cz/habarta/typescript/generator/ext/OnePossiblePropertyValueAssigningExtensionTest.java
index c7ccc6bcf..d7f747b2f 100644
--- a/typescript-generator-core/src/test/java/cz/habarta/typescript/generator/ext/OnePossiblePropertyValueAssigningExtensionTest.java
+++ b/typescript-generator-core/src/test/java/cz/habarta/typescript/generator/ext/OnePossiblePropertyValueAssigningExtensionTest.java
@@ -18,7 +18,7 @@ public class OnePossiblePropertyValueAssigningExtensionTest {
     private static final String BASE_PATH = "/ext/OnePossiblePropertyValueAssigningExtensionTest-";
 
     @JsonTypeInfo(use = JsonTypeInfo.Id.NAME, property = "discriminator")
-    static class BaseClass {
+    abstract static class BaseClass {
 
         @JsonProperty
         private Long field1;
@@ -87,4 +87,4 @@ private String readResource(String suffix) {
         return Utils.readString(getClass().getResourceAsStream(BASE_PATH + suffix), "\n");
     }
 
-}
\ No newline at end of file
+}