test: add comments to new test cases

tests/rules/deprecation.test.ts

@@ -169,6 +169,7 @@ ruleTester.run('deprecation', rule, {
     getValidTestCase(`
       const component = <Component/>;
     `),
+    // Class method with multiple signatures
     getValidTestCase(`
     class Class {
       method(param: string): void;
@@ -180,6 +181,9 @@ ruleTester.run('deprecation', rule, {
     const obj = new Class();
     obj.method('');
   `),
+  // Interface with multiple signatures, extending a class
+  // This notation used to be mentioned in the TypeScript handbook
+  // See https://www.typescriptlang.org/docs/handbook/classes.html#using-a-class-as-an-interface
   getValidTestCase(`
     class Class {}
     interface Interface extends Class {
@@ -189,6 +193,7 @@ ruleTester.run('deprecation', rule, {
     const obj: Interface = { method(args: any) {} };
     obj.method('');
   `),
+  // Class with multiple method signatures, extending an interface
   getValidTestCase(`
     interface Interface {}
     class Class implements Interface {