diff --git a/index.d.ts b/index.d.ts
new file mode 100644
index 0000000..a51fc46
--- /dev/null
+++ b/index.d.ts
@@ -0,0 +1,103 @@
+declare module 'mock-spawn' {
+  import { SpawnOptions } from 'child_process';
+  import { EventEmitter } from 'events';
+  /**
+   * Returns a function that can be plugged into `child_process` as a replacement for `spawn`.
+   *
+   * @param verbose - True to see additional debug messages from this library.
+   * @returns A MockSpawn function.
+   */
+  export default function(verbose?: boolean): Main;
+
+  interface Runner {
+    /**
+     * Runs the sequence code calling `cb` when it is done.
+     */
+    (cb: (exitCode: number) => void): void;
+
+    /**
+     * A chainable function that sets the verbosity of the `Runner`.
+     *
+     * @remarks
+     * Used internally.
+     *
+     * @param verbose - True to see additional debug messages from this library.
+     * @returns the chained Runner.
+     */
+    setVerbose?(verbose: boolean): Runner;
+  }
+
+  interface Strategy {
+    (command: string, args: string[], opts: SpawnOptions):
+      | Runner
+      | undefined
+      | null;
+    /**
+     * Enables the `sequence` strategy and calls the runner function supplied at the specific point in the sequence.
+     *
+     * @remarks
+     * Do not mix `sequence.add` and `setStrategy` calls for a specific run.
+     *
+     * @param fn - The runner function to use. The nth call to `add` plugs a runner function for the nth invocation to `spawn`.
+     */
+    add(fn: Runner | { throws: Error }): void;
+  }
+
+  interface Signals {
+    [signal: string]: boolean;
+  }
+
+  /* eslint-disable require-jsdoc */
+  class MockProcess extends EventEmitter {
+    public constructor(runner: Runner, signals: Signals);
+    public command: string;
+    public args: string[];
+    public opts: SpawnOptions;
+    public exitCode: number;
+    public signal: string;
+  }
+
+  interface Main {
+    (command: string, args?: string[], opts?: SpawnOptions): MockProcess;
+    /**
+     * A strategy object that has an `add` function allowing runner functions to be appended in sequence.
+     */
+    readonly sequence: Strategy;
+    /**
+     * Array of mock process objects that you can use to inspect how your library under test invoked `spawn`. Every object has the following properties available.
+     *
+     * @returns An array of mock process objects.
+     */
+    readonly calls: MockProcess[];
+    /**
+     * Sets the default processing of all spawn invocations to use the runner function specified.
+     *
+     * @param fn - A runner function to handler default processing.
+     */
+    setDefault(fn: Runner): void;
+    /**
+     * Sets `fn` as the strategy that will return runner functions on demand.
+     *
+     * @remarks
+     * Do not mix `sequence.add` and `setStrategy` calls for a specific run.
+     *
+     * @param fn - The function to be used as the strategy function.
+     */
+    setStrategy(fn: Strategy): void;
+    /**
+     * Returns a runner function that exits with the specified code and writes specific data to the output and error streams.
+     *
+     * @param exitCode - Exit code for the process.
+     * @param stdout - The data to be written to standard output.
+     * @param stderr - The data to be written to standard error.
+     * @returns A runner function.
+     */
+    simple(exitCode: number, stdout?: string, stderr?: string): Runner;
+    /**
+     * Sets `obj` as a lookup table for whether to exit. If the value is `true`, then the runner will emit `exit` with code `null` and signal `<signal>`.
+     *
+     * @param obj - the object with signal names and whether to exit.
+     */
+    setSignals(obj: Signals): void;
+  }
+}