jscodeshift-test-describe-class-prototype.js

import _ from "lodash";

/**
 * jscodeshift codemod to rename Jest test files for classes from:
 * ```
 * describe(MyCat, () => {
 *   describe("meow", () => { ... });
 * });
 * ```
 * to:
 * ```
 * describe(MyCat, () => {
 *   describe(MyCat.prototype.meow, () => { ... });
 * });
 * ```
 */
export default function transformer(file, { jscodeshift: j }) {
  return j(file.source)
    .find(j.CallExpression, {
      callee: { type: "Identifier", name: "describe" },
    })
    .forEach((topPath) =>
      j(topPath.node.arguments)
        .find(j.CallExpression, { callee: { type: "Identifier", name: "describe" } })
        .filter((path) => path.node.arguments[0].type === "StringLiteral")
        .find(j.Literal)
        .at(0)
        .replaceWith((node) => {
          const className = topPath.node.arguments[0].name;
          const methodName = node.value.value;
          assertValidMethodName(methodName);

          const methodIdenfier = `${className}.prototype.${methodName}`;
          return j.identifier(methodIdenfier);
        })
    )
    .toSource();
}

function assertValidMethodName(string) {
  if (containsWhitespace(string)) {
    throw new Error(`"${string}" contains whitespace!`);
  }
  if (!isCamelCase(string)) {
    throw new Error(`"${string}" is not in camel case!`);
  }
  return true;
}

function containsWhitespace(string) {
  return /\s/g.test(string);
}

function isCamelCase(str) {
  return _.camelCase(str) === str;
}