Make tests happy

types/jss/index.d.ts

@@ -105,11 +105,11 @@ export interface RuleOptions {
 }
 export declare class SheetsRegistry {
     constructor();
-    registry: ReadonlyArray<StyleSheet<any>>;
+    registry: ReadonlyArray<StyleSheet>;
     readonly index: number;
-    add(sheet: StyleSheet<any>): void;
+    add(sheet: StyleSheet): void;
     reset(): void;
-    remove(sheet: StyleSheet<any>): void;
+    remove(sheet: StyleSheet): void;
     toString(options?: ToCssOptions): string;
 }
 declare class JSS {

types/jss/jss-tests.ts

@@ -92,7 +92,11 @@ sheetsRegistry.add(styleSheet);
 const secondStyleSheet = jss.createStyleSheet(
 	{
 		ruleWithMockObservable: {
-			subscribe() {}
+			subscribe() {
+				return {
+					unsubscribe() {}
+				};
+			}
 		},
 		container2: {
 			display: 'flex',