3 files changed, 21 insertions, 2 deletions
diff --git a/src/image.ts b/src/image.ts
index 8aeab602..9fe7f603 100644
--- a/src/image.ts
+++ b/src/image.ts
@@ -2,6 +2,7 @@ import type { Faker } from '.';
 import { LoremPicsum } from './image_providers/lorempicsum';
 import { Lorempixel } from './image_providers/lorempixel';
 import { Unsplash } from './image_providers/unsplash';
+import type { MethodsOf } from './utils/types';
 
 /**
  * Module to generate placeholder images.
@@ -40,7 +41,7 @@ export class Image {
    * faker.image.image(1234, 2345, true) // 'http://loremflickr.com/1234/2345/nature?56789'
    */
   image(width?: number, height?: number, randomize?: boolean): string {
-    const categories = [
+    const categories: MethodsOf<Image, Image['image']> = [
       'abstract',
       'animals',
       'business',
diff --git a/src/image_providers/lorempixel.ts b/src/image_providers/lorempixel.ts
index 914f1066..50e48ede 100644
--- a/src/image_providers/lorempixel.ts
+++ b/src/image_providers/lorempixel.ts
@@ -1,4 +1,5 @@
 import type { Faker } from '..';
+import type { MethodsOf } from '../utils/types';
 
 /**
  * Module to generate links to random images on `https://lorempixel.com/`.
@@ -14,7 +15,7 @@ export class Lorempixel {
    * @param randomize Whether to append a seed to the url. Defaults to `false`.
    */
   image(width?: number, height?: number, randomize?: boolean): string {
-    const categories = [
+    const categories: MethodsOf<Lorempixel, Lorempixel['image']> = [
       'abstract',
       'animals',
       'business',
diff --git a/src/utils/types.ts b/src/utils/types.ts
new file mode 100644
index 00000000..705d02d1
--- /dev/null
+++ b/src/utils/types.ts
@@ -0,0 +1,17 @@
+/**
+ * Type that represents a single method/function name of the given type.
+ */
+export type MethodOf<
+  ObjectType,
+  Signature extends (...args) => unknown = (...args) => unknown
+> = {
+  [Key in keyof ObjectType]: ObjectType[Key] extends Signature ? Key : never;
+}[keyof ObjectType];
+
+/**
+ * Type that represents all method/function names of the given type.
+ */
+export type MethodsOf<
+  ObjectType,
+  Signature extends (...args) => unknown = (...args) => unknown
+> = ReadonlyArray<MethodOf<ObjectType, Signature>>;