diff --git a/integration/ocean/ConsumeAssetBrizo.test.ts b/integration/ocean/ConsumeAssetBrizo.test.ts
index 44d4197..6f50886 100644
--- a/integration/ocean/ConsumeAssetBrizo.test.ts
+++ b/integration/ocean/ConsumeAssetBrizo.test.ts
@@ -38,7 +38,7 @@ describe("Consume Asset (Brizo)", () => {
 
         const steps = []
         agreementId = await ocean.assets.order(ddo.id, accessService.serviceDefinitionId, consumer)
-            .next(step => steps.push(step))
+            .next((step) => steps.push(step))
 
         assert.isDefined(agreementId)
         assert.deepEqual(steps, [0, 1, 2, 3])
diff --git a/src/ocean/OceanAssets.ts b/src/ocean/OceanAssets.ts
index 753af1f..1b81b64 100644
--- a/src/ocean/OceanAssets.ts
+++ b/src/ocean/OceanAssets.ts
@@ -212,7 +212,7 @@ export class OceanAssets extends Instantiable {
         consumer: Account,
     ): SubscribablePromise<OrderProgressStep, string> {
 
-        return new SubscribablePromise(async observer => {
+        return new SubscribablePromise(async (observer) => {
             const oceanAgreements = this.ocean.agreements
 
             this.logger.log("Asking for agreement signature")
diff --git a/src/utils/SubscribableObserver.ts b/src/utils/SubscribableObserver.ts
new file mode 100644
index 0000000..3d96317
--- /dev/null
+++ b/src/utils/SubscribableObserver.ts
@@ -0,0 +1,42 @@
+export class SubscribableObserver<T, P> {
+    public completed: boolean = false
+    private subscriptions = new Set<{onNext?: (next: T) => void, onComplete?: (complete: P) => void, onError?: (error: any) => void}>()
+
+    public subscribe(onNext?: (next: T) => void, onComplete?: (complete: P) => void, onError?: (error: any) => void) {
+        if (this.completed) {
+            throw new Error("Observer completed.")
+        }
+        const subscription = {onNext, onComplete, onError}
+        this.subscriptions.add(subscription)
+
+        return {
+            unsubscribe: () => this.subscriptions.delete(subscription),
+        }
+    }
+
+    public next(next?: T): void {
+        this.emit("onNext", next)
+    }
+
+    public complete(resolve?: P): void {
+        this.emit("onComplete", resolve)
+        this.unsubscribe()
+    }
+
+    public error(error?: any): void {
+        this.emit("onError", error)
+        this.unsubscribe()
+    }
+
+    private emit(type: "onNext" | "onComplete" | "onError", value: any) {
+        Array.from(this.subscriptions)
+            .map((subscription) => subscription[type])
+            .filter((callback: any) => callback && typeof callback === "function")
+            .forEach((callback: any) => callback(value))
+    }
+
+    private unsubscribe() {
+        this.completed = true
+        this.subscriptions.clear()
+    }
+}
diff --git a/src/utils/SubscribablePromise.ts b/src/utils/SubscribablePromise.ts
index bc0b240..15f3d4f 100644
--- a/src/utils/SubscribablePromise.ts
+++ b/src/utils/SubscribablePromise.ts
@@ -1,45 +1,4 @@
-export class SubscribableObserver<T, P> {
-    public completed: boolean = false
-    private subscriptions = new Set<{onNext?: (next: T) => void, onComplete?: (complete: P) => void, onError?: (error: any) => void}>()
-
-    subscribe(onNext?: (next: T) => void, onComplete?: (complete: P) => void, onError?: (error: any) => void) {
-        if (this.completed) {
-            throw new Error("Observer completed.")
-        }
-        const subscription = {onNext, onComplete, onError}
-        this.subscriptions.add(subscription)
-
-        return {
-            unsubscribe: () => this.subscriptions.delete(subscription),
-        }
-    }
-
-    next(next?: T): void {
-        this.emit('onNext', next)
-    }
-
-    complete(resolve?: P): void {
-        this.emit('onComplete', resolve)
-        this.unsubscribe()
-    }
-
-    error(error?: any): void {
-        this.emit('onError', error)
-        this.unsubscribe()
-    }
-
-    private emit(type: 'onNext' | 'onComplete' | 'onError', value: any) {
-        Array.from(this.subscriptions)
-            .map(subscription => subscription[type])
-            .filter(callback => callback && typeof callback === 'function')
-            .forEach(callback => callback(value))
-    }
-
-    private unsubscribe() {
-        this.completed = true
-        this.subscriptions.clear()
-    }
-}
+import { SubscribableObserver } from "./SubscribableObserver"
 
 export class SubscribablePromise<T extends any, P extends any> {
     private observer = new SubscribableObserver<T, P>()
@@ -48,7 +7,7 @@ export class SubscribablePromise<T extends any, P extends any> {
             setTimeout(() => {
                 this.observer
                     .subscribe(undefined, resolve, reject)
-            })
+            }, 0)
         }),
         this,
     )
@@ -57,31 +16,31 @@ export class SubscribablePromise<T extends any, P extends any> {
         const execution = executor(this.observer)
 
         Promise.resolve(execution as any)
-            .then(result => {
-                if (Promise.resolve(execution as any) == execution) {
+            .then((result) => {
+                if (Promise.resolve(execution as any) === execution) {
                     this.observer.complete(result)
                 }
             })
     }
 
-    subscribe(onNext: (next: T) => void) {
+    public subscribe(onNext: (next: T) => void) {
         return this.observer.subscribe(onNext)
     }
 
-    next(onNext: (next: T) => void) {
+    public next(onNext: (next: T) => void) {
         this.observer.subscribe(onNext)
         return this
     }
 
-    then(onfulfilled?: (value: P) => any, onrejected?: (error: any) => any) {
+    public then(onfulfilled?: (value: P) => any, onrejected?: (error: any) => any) {
         return Object.assign(this.promise.then(onfulfilled, onrejected), this)
     }
 
-    catch(onrejected?: (error: any) => any) {
+    public catch(onrejected?: (error: any) => any) {
         return Object.assign(this.promise.catch(onrejected), this)
     }
 
-    finally(onfinally?: () => any) {
+    public finally(onfinally?: () => any) {
         return Object.assign(this.promise.finally(onfinally), this)
     }
 }
diff --git a/src/utils/index.ts b/src/utils/index.ts
index 52920bd..d8cf9bb 100644
--- a/src/utils/index.ts
+++ b/src/utils/index.ts
@@ -4,3 +4,4 @@ export * from "./ConversionTypeHelpers"
 export * from "./GeneratorHelpers"
 export * from "./DDOHelpers"
 export * from "./SubscribablePromise"
+export * from "./SubscribableObserver"
diff --git a/test/utils/SubscribableObserver.test.ts b/test/utils/SubscribableObserver.test.ts
new file mode 100644
index 0000000..2681f05
--- /dev/null
+++ b/test/utils/SubscribableObserver.test.ts
@@ -0,0 +1,76 @@
+import { assert, expect, spy, use } from "chai"
+import * as spies from "chai-spies"
+
+import { SubscribableObserver} from "../../src/utils/SubscribableObserver"
+
+use(spies)
+
+describe("SubscribableObserver", () => {
+
+    describe("#subscribe()", () => {
+
+        it("should be able to add a subcription", async () => {
+            const observer = new SubscribableObserver()
+            const subscription = observer.subscribe()
+
+            assert.isDefined(subscription.unsubscribe)
+            assert.typeOf(subscription.unsubscribe, "function")
+        })
+
+        it("should be able to unsubscribe", async () => {
+            const observer = new SubscribableObserver()
+            const subscription = observer.subscribe()
+
+            subscription.unsubscribe()
+        })
+    })
+
+    describe("#next()", () => {
+
+        it("should be able to emit next value", async () => {
+            const onNextSpy = spy()
+            const observer = new SubscribableObserver()
+            observer.subscribe(onNextSpy)
+
+            observer.next("test")
+            expect(onNextSpy).to.has.been.called.with("test")
+
+            observer.next("test")
+            expect(onNextSpy).to.has.been.called.exactly(2)
+        })
+    })
+
+    describe("#complete()", () => {
+
+        it("should be able to complete", async () => {
+            const onCompleteSpy = spy()
+            const observer = new SubscribableObserver()
+            observer.subscribe(undefined, onCompleteSpy)
+
+            observer.complete("test")
+            expect(onCompleteSpy).to.has.been.called.with("test")
+
+            observer.complete("test")
+            expect(onCompleteSpy).to.has.been.called.exactly(1)
+
+            assert.isTrue(observer.completed)
+        })
+    })
+
+    describe("#error()", () => {
+
+        it("should be able to emit a error", async () => {
+            const onErrorSpy = spy()
+            const observer = new SubscribableObserver()
+            observer.subscribe(undefined, undefined, onErrorSpy)
+
+            observer.error("test")
+            expect(onErrorSpy).to.has.been.called.with("test")
+
+            observer.error("test")
+            expect(onErrorSpy).to.has.been.called.exactly(1)
+
+            assert.isTrue(observer.completed)
+        })
+    })
+})
diff --git a/test/utils/SubscribablePromise.test.ts b/test/utils/SubscribablePromise.test.ts
index edfbfab..5948a2f 100644
--- a/test/utils/SubscribablePromise.test.ts
+++ b/test/utils/SubscribablePromise.test.ts
@@ -1,80 +1,10 @@
 import { assert, expect, spy, use } from "chai"
 import * as spies from "chai-spies"
 
-import { SubscribableObserver, SubscribablePromise } from "../../src/utils/SubscribablePromise"
+import { SubscribablePromise } from "../../src/utils/SubscribablePromise"
 
 use(spies)
 
-describe("SubscribableObserver", () => {
-
-    describe("#subscribe()", () => {
-
-        it("should be able to add a subcription", async () => {
-            const observer = new SubscribableObserver()
-            const subscription = observer.subscribe()
-
-            assert.isDefined(subscription.unsubscribe)
-            assert.typeOf(subscription.unsubscribe, 'function')
-        })
-
-        it("should be able to unsubscribe", async () => {
-            const observer = new SubscribableObserver()
-            const subscription = observer.subscribe()
-
-            subscription.unsubscribe()
-        })
-    })
-
-    describe("#next()", () => {
-
-        it("should be able to emit next value", async () => {
-            const onNextSpy = spy()
-            const observer = new SubscribableObserver()
-            observer.subscribe(onNextSpy)
-
-            observer.next('test')
-            expect(onNextSpy).to.has.been.called.with('test')
-
-            observer.next('test')
-            expect(onNextSpy).to.has.been.called.exactly(2)
-        })
-    })
-
-    describe("#complete()", () => {
-
-        it("should be able to complete", async () => {
-            const onCompleteSpy = spy()
-            const observer = new SubscribableObserver()
-            observer.subscribe(undefined, onCompleteSpy)
-
-            observer.complete('test')
-            expect(onCompleteSpy).to.has.been.called.with('test')
-
-            observer.complete('test')
-            expect(onCompleteSpy).to.has.been.called.exactly(1)
-
-            assert.isTrue(observer.completed)
-        })
-    })
-
-    describe("#error()", () => {
-
-        it("should be able to emit a error", async () => {
-            const onErrorSpy = spy()
-            const observer = new SubscribableObserver()
-            observer.subscribe(undefined, undefined, onErrorSpy)
-
-            observer.error('test')
-            expect(onErrorSpy).to.has.been.called.with('test')
-
-            observer.error('test')
-            expect(onErrorSpy).to.has.been.called.exactly(1)
-
-            assert.isTrue(observer.completed)
-        })
-    })
-})
-
 describe("SubscribablePromise", () => {
 
     it("should work", async () => {
@@ -91,19 +21,19 @@ describe("SubscribablePromise", () => {
 
             assert.isDefined(subscription)
             assert.isDefined(subscription.unsubscribe)
-            assert.typeOf(subscription.unsubscribe, 'function')
+            assert.typeOf(subscription.unsubscribe, "function")
         })
 
         it("should listen the next values", (done) => {
             const onNextSpy = spy()
-            const subscribible = new SubscribablePromise(observer => {
-                setTimeout(() => observer.next('test'), 10)
-                setTimeout(() => observer.next('test'), 20)
+            const subscribible = new SubscribablePromise((observer) => {
+                setTimeout(() => observer.next("test"), 10)
+                setTimeout(() => observer.next("test"), 20)
             })
             subscribible.subscribe(onNextSpy)
 
             setTimeout(() => {
-                expect(onNextSpy).to.has.been.called.with('test')
+                expect(onNextSpy).to.has.been.called.with("test")
                 expect(onNextSpy).to.has.been.called.exactly(2)
                 done()
             }, 100)
@@ -115,9 +45,9 @@ describe("SubscribablePromise", () => {
         it("should resolve", (done) => {
             const onCompleteSpy = spy()
             const onFinallySpy = spy()
-            const subscribible = new SubscribablePromise(observer => {
-                setTimeout(() => observer.next('test'), 10)
-                setTimeout(() => observer.complete('test'), 20)
+            const subscribible = new SubscribablePromise((observer) => {
+                setTimeout(() => observer.next("test"), 10)
+                setTimeout(() => observer.complete("test"), 20)
             })
 
             subscribible
@@ -125,7 +55,7 @@ describe("SubscribablePromise", () => {
                 .finally(onFinallySpy)
 
             setTimeout(() => {
-                expect(onCompleteSpy).to.has.been.called.with('test')
+                expect(onCompleteSpy).to.has.been.called.with("test")
                 expect(onCompleteSpy).to.has.been.called.exactly(1)
                 expect(onFinallySpy).to.has.been.called.exactly(1)
                 done()
@@ -138,9 +68,9 @@ describe("SubscribablePromise", () => {
         it("should catch the error", (done) => {
             const onErrorSpy = spy()
             const onFinallySpy = spy()
-            const subscribible = new SubscribablePromise(observer => {
-                setTimeout(() => observer.next('test'), 10)
-                setTimeout(() => observer.error('test'), 20)
+            const subscribible = new SubscribablePromise((observer) => {
+                setTimeout(() => observer.next("test"), 10)
+                setTimeout(() => observer.error("test"), 20)
             })
 
             subscribible
@@ -148,7 +78,7 @@ describe("SubscribablePromise", () => {
                 .finally(onFinallySpy)
 
             setTimeout(() => {
-                expect(onErrorSpy).to.has.been.called.with('test')
+                expect(onErrorSpy).to.has.been.called.with("test")
                 expect(onErrorSpy).to.has.been.called.exactly(1)
                 expect(onFinallySpy).to.has.been.called.exactly(1)
                 done()
@@ -158,38 +88,38 @@ describe("SubscribablePromise", () => {
 
     it("should be able to subscribe and wait for a promise", async () => {
         const onNextSpy = spy()
-        const subscribible = new SubscribablePromise(observer => {
-            setTimeout(() => observer.next('test'), 10)
-            setTimeout(() => observer.next('test'), 20)
-            setTimeout(() => observer.complete('completed'), 30)
+        const subscribible = new SubscribablePromise((observer) => {
+            setTimeout(() => observer.next("test"), 10)
+            setTimeout(() => observer.next("test"), 20)
+            setTimeout(() => observer.complete("completed"), 30)
         })
 
         const result = await subscribible
             .next(onNextSpy)
 
-        expect(onNextSpy).to.has.been.called.with('test')
+        expect(onNextSpy).to.has.been.called.with("test")
         expect(onNextSpy).to.has.been.called.exactly(2)
 
-        assert.equal(result, 'completed')
+        assert.equal(result, "completed")
     })
 
     it("should use the result of a the promise as executor to complete the observer", async () => {
         const onNextSpy = spy()
-        const subscribible = new SubscribablePromise(async observer => {
-            await new Promise(resolve => setTimeout(resolve, 10))
-            observer.next('test')
-            await new Promise(resolve => setTimeout(resolve, 10))
-            observer.next('test')
-            await new Promise(resolve => setTimeout(resolve, 10))
-            return 'completed'
+        const subscribible = new SubscribablePromise(async (observer) => {
+            await new Promise((resolve) => setTimeout(resolve, 10))
+            observer.next("test")
+            await new Promise((resolve) => setTimeout(resolve, 10))
+            observer.next("test")
+            await new Promise((resolve) => setTimeout(resolve, 10))
+            return "completed"
         })
 
         const result = await subscribible
             .next(onNextSpy)
 
-        expect(onNextSpy).to.has.been.called.with('test')
+        expect(onNextSpy).to.has.been.called.with("test")
         expect(onNextSpy).to.has.been.called.exactly(2)
 
-        assert.equal(result, 'completed')
+        assert.equal(result, "completed")
     })
 })
diff --git a/tslint.json b/tslint.json
index 0371ac2..23eb96a 100644
--- a/tslint.json
+++ b/tslint.json
@@ -12,6 +12,7 @@
       true,
       "never"
     ],
+    "no-empty": [true, "allow-empty-catch", "allow-empty-functions"],
     "ordered-imports": false
   },
   "rulesDirectory": []