Can't sendKeys() to TinyMCE with Selenium WebDriver

Yes, as what Richard says, this is a duplicate of How to input text into tinceMCE editior using selenium/webdriver.

For your specific code, I'd suggest

• Try different locator for mceContentBody, e.g use By.cssSelector(".mceContentBody"), By.cssSelector("body"), etc.

• Click the body first before sending keys.

driver.findElement(By.tagName("body")).click().sendKeys("YOOOO");

• Set innerHTML

inputWebDriver.switchTo().frame("input-data_ifr");
WebElement element = inputWebDriver.findElement(By.cssSelector("body"));
(JavascriptExecutor)driver.executeScript("arguments[0].innerHTML = '<h1>Set text using innerHTML</h1>'", element);

• Use TinyMCE's native API

// no need to switch iframe
(JavascriptExecutor)driver.executeScript("tinyMCE.activeEditor.setContent('<h1>Native API text</h1> TinyMCE')");

Further reading: Test WYSIWYG editors using Selenium WebDriver