diff --git a/examples/.gitkeep b/examples/.gitkeep
new file mode 100644
index 0000000..e69de29
diff --git a/src/__test__/fetchers/common.test.ts b/src/__test__/fetchers/common.test.ts
new file mode 100644
index 0000000..c067491
--- /dev/null
+++ b/src/__test__/fetchers/common.test.ts
@@ -0,0 +1,48 @@
+import { makeFullUrl } from "@/fetchers/common";
+import { describe, expect, it } from "vitest";
+
+describe("makeFullUrl()", () => {
+  it('should pass normal url if no options', () => {
+    expect(makeFullUrl('https://example.com/hello/world')).toEqual("https://example.com/hello/world")
+    expect(makeFullUrl('https://example.com/hello/world?a=b')).toEqual("https://example.com/hello/world?a=b")
+    expect(makeFullUrl('https://example.com/hello/world?a=b#hello')).toEqual("https://example.com/hello/world?a=b#hello")
+    expect(makeFullUrl('https://example.com/hello/world#hello')).toEqual("https://example.com/hello/world#hello")
+  })
+
+  it('should append baseurl correctly', () => {
+    const correctResult = "https://example.com/hello/world";
+    expect(makeFullUrl(correctResult, { baseUrl: '' })).toEqual(correctResult)
+    expect(makeFullUrl('/hello/world', { baseUrl: 'https://example.com' })).toEqual(correctResult)
+    expect(makeFullUrl('/hello/world', { baseUrl: 'https://example.com/' })).toEqual(correctResult)
+    expect(makeFullUrl('hello/world', { baseUrl: 'https://example.com/' })).toEqual(correctResult)
+    expect(makeFullUrl('hello/world', { baseUrl: 'https://example.com' })).toEqual(correctResult)
+    expect(makeFullUrl('/world', { baseUrl: 'https://example.com/hello' })).toEqual(correctResult)
+    expect(makeFullUrl('/world', { baseUrl: 'https://example.com/hello/' })).toEqual(correctResult)
+    expect(makeFullUrl('world', { baseUrl: 'https://example.com/hello/' })).toEqual(correctResult)
+    expect(makeFullUrl('world', { baseUrl: 'https://example.com/hello' })).toEqual(correctResult)
+    expect(makeFullUrl('world?a=b', { baseUrl: 'https://example.com/hello' })).toEqual("https://example.com/hello/world?a=b")
+  })
+
+  it('should throw with invalid baseurl combinations', () => {
+    expect(() => makeFullUrl('example.com/hello/world', { baseUrl: '' })).toThrowError()
+    expect(() => makeFullUrl('/hello/world', { baseUrl: 'example.com' })).toThrowError()
+    expect(() => makeFullUrl('/hello/world', { baseUrl: 'tcp://example.com' })).toThrowError()
+    expect(() => makeFullUrl('/hello/world', { baseUrl: 'tcp://example.com' })).toThrowError()
+  })
+
+  it('should add/merge query parameters', () => {
+    expect(makeFullUrl('https://example.com/hello/world', { query: { a: 'b' } })).toEqual("https://example.com/hello/world?a=b")
+    expect(makeFullUrl('https://example.com/hello/world/', { query: { a: 'b' } })).toEqual("https://example.com/hello/world/?a=b")
+    expect(makeFullUrl('https://example.com', { query: { a: 'b' } })).toEqual("https://example.com/?a=b")
+    expect(makeFullUrl('https://example.com/', { query: { a: 'b' } })).toEqual("https://example.com/?a=b")
+
+    expect(makeFullUrl('https://example.com/hello/world?c=d', { query: { a: 'b' } })).toEqual("https://example.com/hello/world?c=d&a=b")
+    expect(makeFullUrl('https://example.com/hello/world?c=d', { query: {} })).toEqual("https://example.com/hello/world?c=d")
+    expect(makeFullUrl('https://example.com/hello/world?c=d')).toEqual("https://example.com/hello/world?c=d")
+    expect(makeFullUrl('https://example.com/hello/world?c=d', {})).toEqual("https://example.com/hello/world?c=d")
+  })
+  
+  it('should work with a mix of multiple options', () => {
+    expect(makeFullUrl('/hello/world?c=d', { baseUrl: 'https://example.com/', query: { a: 'b' } })).toEqual("https://example.com/hello/world?c=d&a=b")
+  })
+})
diff --git a/src/fetchers/common.ts b/src/fetchers/common.ts
index e0c1780..e31b6d1 100644
--- a/src/fetchers/common.ts
+++ b/src/fetchers/common.ts
@@ -1,10 +1,22 @@
 import { Fetcher, FetcherOptions, UseableFetcher } from '@/fetchers/types';
 
+export type FullUrlOptions = Pick<FetcherOptions, 'query' | 'baseUrl'>;
+
 // make url with query params and base url used correctly
-export function makeFullUrl(url: string, ops?: FetcherOptions): string {
+export function makeFullUrl(url: string, ops?: FullUrlOptions): string {
   // glue baseUrl and rest of url together
-  const fullUrl = ops?.baseUrl ?? '';
-  // TODO make full url
+  let leftSide = ops?.baseUrl ?? '';
+  let rightSide = url;
+
+  // left side should always end with slash, if its set
+  if (leftSide.length > 0 && !leftSide.endsWith('/')) leftSide += '/';
+
+  // right side should never start with slash
+  if (rightSide.startsWith('/')) rightSide = rightSide.slice(1);
+
+  const fullUrl = leftSide + rightSide;
+  if (!fullUrl.startsWith('http://') && !fullUrl.startsWith('https://'))
+    throw new Error(`Invald URL -- URL doesn't start with a http scheme: '${fullUrl}'`);
 
   const parsedUrl = new URL(fullUrl);
   Object.entries(ops?.query ?? {}).forEach(([k, v]) => {