unitTestHelpers.ts

import * as ts from 'typescript';

const printer = ts.createPrinter();

// Create ts.Node from given typescript code.
export const createNode = <T extends ts.Node>(code: string, type: number): [T, ts.SourceFile] => {
    const sourcefile = ts.createSourceFile('test.ts', code, ts.ScriptTarget.ES2015, true);
    const node = fetchNodeFromSourceFile(sourcefile);
    if (node.kind !== type) {
        throw new Error(`TypeScript node created from given code doesn't match expected type, expected: ${type} but compiled: ${node.kind}!`);
    }

    return [node as T, sourcefile];
};

// Get string representation of given TypeScript node.
export const printNode = <T extends ts.Node>(node: T, sourceFile: ts.SourceFile): string => {
    return printer.printNode(ts.EmitHint.Expression, node, sourceFile);
};