code: function completeSpecFiles(argv, _filters) {
          // if user manually defined an empty specFiles array, do not add specFiles from folder
          if (Object.keys(_filters.specFiles).length === 0 && !argv.specFiles) {
              io_1.getAllFiles(specsDir, '.spec.ts').forEach(specFile => _filters.specFiles[specFile] = true);
              return true;
          }
          else {
              let removeOnly = true;
              const removeSpecFiles = {};
              for (const specFile in _filters.specFiles) {
                  let remove = false;
                  let matchStr = specFile;
                  if (specFile.substr(0, 1) === '-') {
                      remove = true;
                      matchStr = specFile.substr(1, specFile.length - 1);
                  }
                  else {
                      removeOnly = false;
                  }
                  if (remove) {
                      delete _filters.specFiles[specFile];
                      removeSpecFiles[matchStr] = true;
                  }
              }
              if (removeOnly) {
                  io_1.getAllFiles(specsDir, '.spec.ts')
                      .filter(specFile => !(specFile in removeSpecFiles))
                      .forEach(specFile => _filters.specFiles[specFile] = true);
              }
          }
          return false;
      }
docs: if no spec files are present in filters, use all spec files in specs folder