Testando

Para testar, Abra o Propt de Comando do Windows e siga as instruções:

Java

> java -version

Se tudo der certo, você verá uma mensagem desse tipo:

java version "1.8.0_202"
Java(TM) SE Runtime Environment (build 1.8.0_202-b08)
Java HotSpot(TM) 64-Bit Server VM (build 25.202-b08, mixed mode)

Node JS

> node -v

Se tudo der certo, você verá uma mensagem desse tipo:

v8.12.0

ADB

> adb --version

Se tudo der certo, você verá uma mensagem desse tipo:

Android Debug Bridge version 1.0.41
Version 29.0.1-5644136
Installed as C:\Users\<Seu Usuario>\AppData\Local\Android\Sdk\platform-tools\adb.exe

Emulator

> emulator -version

Se tudo der certo, você verá uma mensagem desse tipo:

Android emulator version 29.0.11.0 (build_id 5598178) (CL:N/A)
Copyright (C) 2006-2017 The Android Open Source Project and many others.
This program is a derivative of the QEMU CPU emulator (www.qemu.org).

  This software is licensed under the terms of the GNU General Public
  License version 2, as published by the Free Software Foundation, and
  may be copied, distributed, and modified under those terms.

  This program is distributed in the hope that it will be useful,
  but WITHOUT ANY WARRANTY; without even the implied warranty of
  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  GNU General Public License for more details.

React Native

> react-native -v

Se tudo der certo, você verá uma mensagem desse tipo:

react-native-cli: 2.0.1
react-native: n/a - not inside a React Native project directory