import { Injectable } from '@angular/core';

export interface ITubularSettingsProvider {
    put(id: string, value: string): void;
    get(key: string): any;
    delete(key: string): void;
}

@Injectable()
export class TubularSettingsService {

    constructor() {
    }

    public put(id: string, value: string) {
        localStorage.setItem(id, JSON.stringify(value));
    }

    public get(key: string): any {
        return JSON.parse(localStorage.getItem(key)) || false;
    }

    public delete(key: string) {
        localStorage.removeItem(key);
    }
}

import { Injectable } from '@angular/core';

@Injectable()
export class TubularSettingsService {

    constructor() {
    }

    public put(id: string, value: string) {
        localStorage.setItem(id, JSON.stringify(value));
    }

    public get(key: string): any {
        return JSON.parse(localStorage.getItem(key)) || false;
    }

    public delete(key: string): any {
        localStorage.removeItem(key);
    }
}

--- 
+++ 
@@ -1,4 +1,10 @@
 import { Injectable } from '@angular/core';
+
+export interface ITubularSettingsProvider {
+    put(id: string, value: string): void;
+    get(key: string): any;
+    delete(key: string): void;
+}
 
 @Injectable()
 export class TubularSettingsService {
@@ -14,7 +20,7 @@
         return JSON.parse(localStorage.getItem(key)) || false;
     }
 
-    public delete(key: string): any {
+    public delete(key: string) {
         localStorage.removeItem(key);
     }
 }
Add interface for settings provider
