feat: fluent Registry#register function and a Registry#exampleGenerator implementation

Author: holvonixAdvay

README.md

@@ -2,6 +2,7 @@
 
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+`io-ts-fuzzer` lets you generate examples of a given `io-ts` type.
 
 ## Quick Start
 
@@ -30,6 +31,8 @@ function fuzz() {
 }
 ````
 
+## Types Supported
+
 Currently supports:
 
 * `t.number`
@@ -48,13 +51,15 @@ Currently supports:
 
 ## Use Cases
 
-### Verifying Decoder Behavior
+### Generating Conforming Examples and Verifying Decoder Behavior
 
 Given a `d = t.Decoder<I,A>` (aka a `t.Type`), `fuzz.exampleGenerator` will
 build a `t.Encoder<number,A>` that will give example instances of `A`.
 The example instances should all pass on `d.decode`, which should return
 an identical example.  No exceptions should be thrown.
 
+### Fuzzing a Type (TODO)
+
 
 ## License
 

src/registry.ts

@@ -1,10 +1,12 @@
-import { Fuzzer } from './fuzzer';
+import { Fuzzer, ExampleGenerator, exampleGenerator } from './fuzzer';
 import * as t from 'io-ts';
 import { coreFuzzers } from './core/';
 
 export interface Registry {
   // tslint:disable-next-line:no-any
-  register(...vv: Array<Fuzzer<any, t.Decoder<unknown, any>>>): void;
+  register(...vv: Array<Fuzzer<any, t.Decoder<unknown, any>>>): Registry;
+
+  exampleGenerator<T>(d: t.Decoder<unknown, T>): ExampleGenerator<T>;
 
   getFuzzer<T>(
     a: t.Decoder<unknown, T>
@@ -35,11 +37,22 @@ class RegistryC implements Registry {
     Fuzzer<any, t.Decoder<unknown, unknown>>
   > = new Map();
 
+  readonly exampleGenerator: <T>(
+    d: t.Decoder<unknown, T>
+  ) => ExampleGenerator<T>;
+
+  constructor() {
+    this.exampleGenerator = exampleGenerator.bind(null, this) as <T>(
+      d: t.Decoder<unknown, T>
+    ) => ExampleGenerator<T>;
+  }
+
   // tslint:disable-next-line:no-any
   register(...vv: Array<Fuzzer<any, t.Decoder<unknown, any>>>) {
     for (const v of vv) {
       this.fuzzers.set(fuzzerKey(v), v);
     }
+    return this;
   }
 
   getFuzzer<T>(a: t.Decoder<unknown, T>) {

test/test-registry.ts

@@ -20,5 +20,14 @@ describe('registry', () => {
         });
       }
     });
+
+    describe('#exampleGenerator', () => {
+      for (const b of types) {
+        it(`can create an example generator for \`${b.name}\` type`, () => {
+          const r = lib.createCoreRegistry().exampleGenerator(b);
+          assert.ok(r);
+        });
+      }
+    });
   });
 });