diff --git a/__tests__/Inputs.test.ts b/__tests__/Inputs.test.ts
index e7bc3a3..9a942e4 100644
--- a/__tests__/Inputs.test.ts
+++ b/__tests__/Inputs.test.ts
@@ -5,19 +5,39 @@ import { Context } from "@actions/github/lib/context";
 
 
 jest.mock('@actions/core', () => {
-    return {getInput: mockGetInput};
+    return { getInput: mockGetInput };
 });
 
 describe('Inputs', () => {
-    let context: Context
-    let inputs: Inputs
+    let context: Context;
+    let inputs: Inputs;
     beforeEach(() => {
         context = new Context()
         inputs = new Inputs(context)
-        mockGetInput.mockReturnValue("")
     })
-    it('returns token', () => {
+
+    it('token method returns input token', () => {
         mockGetInput.mockReturnValue("42")
         expect(inputs.token).toBe("42")
     })
+
+    describe('tag', () => {
+        it('tag property returns input tag', () => {
+            mockGetInput.mockReturnValue("tag")
+            expect(inputs.tag).toBe("tag")
+        })
+        it('tag property returns context sha when input is empty', () => {
+            mockGetInput.mockReturnValue("")
+            context.ref = "refs/tags/sha-tag"
+            expect(inputs.tag).toBe("sha-tag")
+        })
+        it('tag property returns context sha when input is null', () => {
+            mockGetInput.mockReturnValue(null)
+            context.ref = "refs/tags/sha-tag"
+            expect(inputs.tag).toBe("sha-tag")
+        })
+        it('tag property throws if no tag', () => {
+            expect(() => inputs.tag).toThrow()
+        })
+    })
 })
\ No newline at end of file
diff --git a/src/Inputs.ts b/src/Inputs.ts
index 1bbb202..c3534b4 100644
--- a/src/Inputs.ts
+++ b/src/Inputs.ts
@@ -5,23 +5,23 @@ export class Inputs {
     private context: Context
 
     constructor(context: Context) {
-        this.context = context;
+        this.context = context
     }
 
     get token(): string {
-        return core.getInput('token', {required: true});
+        return core.getInput('token', {required: true})
     }
 
     get tag() : string {
-        const tag = core.getInput('tag');
-        if(tag != null) {
+        const tag = core.getInput('tag')
+        if(tag) {
             return tag;
         }
 
-        const ref = this.context.ref;
-        const tagPath = "refs/tags/";
-        if(ref.startsWith(tagPath)) {
-            return ref.substr(0, tagPath.length);
+        const ref = this.context.ref
+        const tagPath = "refs/tags/"
+        if(ref && ref.startsWith(tagPath)) {
+            return ref.substr(tagPath.length, ref.length)
         }
 
         throw Error("No tag found in ref or input!")
diff --git a/src/Releases.ts b/src/Releases.ts
index a453b73..1fdfef6 100644
--- a/src/Releases.ts
+++ b/src/Releases.ts
@@ -3,12 +3,12 @@ import { GitHub } from "@actions/github";
 import { Response, ReposCreateReleaseResponse } from "@octokit/rest";
 
 export class Releases {
-    context: Context;
-    git: GitHub;
+    context: Context
+    git: GitHub
 
     constructor(context: Context, git: GitHub) {
-        this.context = context;
-        this.git = git;
+        this.context = context
+        this.git = git
     }
 
     async create(tag: string, commitHash?: string): Promise<Response<ReposCreateReleaseResponse>> {