Add naive selector collision test (#74)

contracts/zero-ex/CHANGELOG.json

@@ -1,4 +1,13 @@
 [
+    {
+        "version": "0.12.0",
+        "changes": [
+            {
+                "note": "Add test for selector collisions on the proxy",
+                "pr": 74
+            }
+        ]
+    },
     {
         "timestamp": 1607381756,
         "version": "0.11.1",

contracts/zero-ex/test/features/selector_collision_test.ts

@@ -0,0 +1,29 @@
+import { blockchainTests, constants, expect } from '@0x/contracts-test-utils';
+import { MethodAbi } from 'ethereum-types';
+
+import * as wrappers from '../../src/wrappers';
+
+blockchainTests('Selector collision test', env => {
+    it('Function selectors do not collide', () => {
+        const selectorToSignature: { [selector: string]: string } = {};
+        for (const wrapper of Object.values(wrappers)) {
+            if (typeof wrapper === 'function') {
+                const contract = new wrapper(constants.NULL_ADDRESS, env.provider, env.txDefaults);
+                contract.abi
+                    .filter(abiDef => abiDef.type === 'function')
+                    .map(method => {
+                        const methodName = (method as MethodAbi).name;
+                        const selector = contract.getSelector(methodName);
+                        const signature = contract.getFunctionSignature(methodName);
+                        if (selectorToSignature[selector]) {
+                            expect(
+                                signature,
+                                `Selectors collide: ${signature}, ${selectorToSignature[selector]}`,
+                            ).to.equal(selectorToSignature[selector]);
+                        }
+                        selectorToSignature[selector] = signature;
+                    });
+            }
+        }
+    });
+});