diff --git a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/AbstractJavaCodegen.java b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/AbstractJavaCodegen.java
index fa2dc09669df..872d954d3fa7 100644
--- a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/AbstractJavaCodegen.java
+++ b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/AbstractJavaCodegen.java
@@ -85,7 +85,8 @@ public abstract class AbstractJavaCodegen extends DefaultCodegen implements Code
     protected String licenseUrl = "http://unlicense.org";
     protected String projectFolder = "src/main";
     protected String projectTestFolder = "src/test";
-    protected String sourceFolder = projectFolder + File.separator + "java";
+    // this must not be OS-specific
+    protected String sourceFolder = projectFolder + "/java";
     protected String testFolder = projectTestFolder + "/java";
     protected boolean fullJavaUtil;
     protected boolean discriminatorCaseSensitive = true; // True if the discriminator value lookup should be case-sensitive.
diff --git a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/GroovyClientCodegen.java b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/GroovyClientCodegen.java
index 95b11793cdf5..c512607cf7db 100644
--- a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/GroovyClientCodegen.java
+++ b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/GroovyClientCodegen.java
@@ -60,7 +60,8 @@ public GroovyClientCodegen() {
         languageSpecificPrimitives.add("File");
         languageSpecificPrimitives.add("Map");
 
-        sourceFolder = projectFolder + File.separator +"groovy";
+        // this must not be OS-specific
+        sourceFolder = projectFolder + "/groovy";
         outputFolder = "generated-code/groovy";
         modelTemplateFiles.put("model.mustache", ".groovy");
         apiTemplateFiles.put("api.mustache", ".groovy");
diff --git a/modules/openapi-generator/src/test/java/org/openapitools/codegen/java/AbstractJavaCodegenTest.java b/modules/openapi-generator/src/test/java/org/openapitools/codegen/java/AbstractJavaCodegenTest.java
index 6ba9e4b67f83..800eb90a3ee0 100644
--- a/modules/openapi-generator/src/test/java/org/openapitools/codegen/java/AbstractJavaCodegenTest.java
+++ b/modules/openapi-generator/src/test/java/org/openapitools/codegen/java/AbstractJavaCodegenTest.java
@@ -42,27 +42,27 @@ public class AbstractJavaCodegenTest {
 
     @Test
     public void toEnumVarNameShouldNotShortenUnderScore() throws Exception {
-        Assert.assertEquals("UNDERSCORE", fakeJavaCodegen.toEnumVarName("_", "String"));
-        Assert.assertEquals("__", fakeJavaCodegen.toEnumVarName("__", "String"));
-        Assert.assertEquals("__", fakeJavaCodegen.toEnumVarName("_,.", "String"));
+        Assert.assertEquals(fakeJavaCodegen.toEnumVarName("_", "String"), "UNDERSCORE");
+        Assert.assertEquals(fakeJavaCodegen.toEnumVarName("__", "String"), "__");
+        Assert.assertEquals(fakeJavaCodegen.toEnumVarName("_,.", "String"), "__");
     }
 
     @Test
     public void toVarNameShouldAvoidOverloadingGetClassMethod() throws Exception {
-        Assert.assertEquals("propertyClass", fakeJavaCodegen.toVarName("class"));
-        Assert.assertEquals("propertyClass", fakeJavaCodegen.toVarName("_class"));
-        Assert.assertEquals("propertyClass", fakeJavaCodegen.toVarName("__class"));
+        Assert.assertEquals(fakeJavaCodegen.toVarName("class"), "propertyClass");
+        Assert.assertEquals(fakeJavaCodegen.toVarName("_class"), "propertyClass");
+        Assert.assertEquals(fakeJavaCodegen.toVarName("__class"), "propertyClass");
     }
 
     @Test
     public void toModelNameShouldUseProvidedMapping() throws Exception {
         fakeJavaCodegen.importMapping().put("json_myclass", "com.test.MyClass");
-        Assert.assertEquals("com.test.MyClass", fakeJavaCodegen.toModelName("json_myclass"));
+        Assert.assertEquals(fakeJavaCodegen.toModelName("json_myclass"), "com.test.MyClass");
     }
 
     @Test
     public void toModelNameUsesPascalCase() throws Exception {
-        Assert.assertEquals("JsonAnotherclass", fakeJavaCodegen.toModelName("json_anotherclass"));
+        Assert.assertEquals(fakeJavaCodegen.toModelName("json_anotherclass"), "JsonAnotherclass");
     }
 
     @Test
@@ -602,6 +602,20 @@ public void maplikeDefaultValueForModelWithStringToModelMapping() {
         Assert.assertEquals(defaultValue, "new HashMap<String, ComplexModel>()", "Expected string-ref map aliased model to default to new HashMap<String, ComplexModel>()");
     }
 
+    @Test
+    public void srcMainFolderShouldNotBeOperatingSystemSpecificPaths() {
+        // it's not responsibility of the generator to fix OS-specific paths. This is left to template manager.
+        // This path must be non-OS-specific for expectations in source outputs (e.g. gradle build files)
+        Assert.assertEquals(fakeJavaCodegen.getSourceFolder(), "src/main/java");
+    }
+
+    @Test
+    public void srcTestFolderShouldNotBeOperatingSystemSpecificPaths() {
+        // it's not responsibility of the generator to fix OS-specific paths. This is left to template manager.
+        // This path must be non-OS-specific for expectations in source outputs (e.g. gradle build files)
+        Assert.assertEquals(fakeJavaCodegen.getTestFolder(), "src/test/java");
+    }
+
     private static Schema<?> createObjectSchemaWithMinItems() {
         return new ObjectSchema()
                 .addProperties("id", new IntegerSchema().format("int32"))