Scala IDE: object scalatest is not a member of package org - eclipse

Question

I'm trying to use Scala IDE. I'm totally new to Scala.
HelloSpec.scala:
import org.scalatest._
class HelloSpec extends FlatSpec with Matchers {
"The Hello object" should "say hello" in {
Hello.greeting shouldEqual "hello"
}
}
import org.scalatest._ is marked by an error:
object scalatest is not a member of package org
I've tried to google it a lot but still don't understand what's wrong. My project structure looks right:
src/main/scala:
----Hello.scala
src/test/scala:
----HelloSpec.scala
build.sbt
plugins.sbt
build.sbt:
import Dependencies._
ThisBuild / scalaVersion := "2.12.8"
ThisBuild / version := "0.1.0-SNAPSHOT"
ThisBuild / organization := "com.example"
ThisBuild / organizationName := "example"
lazy val root = (project in file("."))
.settings(
name := "$name$",
libraryDependencies += scalaTest % Test
)
plugins.sbt:
addSbtPlugin("com.typesafe.sbteclipse" % "sbteclipse-plugin" % "4.0.0")
I haven't build the project BTW. Is that could be the reason? I don't know how to build the project from Scala IDE, and if I build it from Windows Command Prompt then it doesn't influence Scala IDE.

Answer 1

I assume your project structure is as below,
src/
main/
resources/
<files to include in main jar here>
scala/
<main Scala sources>
test/
resources
<files to include in test jar here>
scala/
<test Scala sources>
build.sbt
plugins.sbt
This is simple hello class
object Hello {
def greeting: String = {
"hello"
}
}
I created the unit testing as below
import org.scalatest._
class HelloSpec extends FlatSpec with Matchers {
"The Hello object" should "say hello" in {
Hello.greeting shouldEqual "hello"
}
}
So, you need just to add scala test in dependcies. Below is simply sbt file
name := "Hello Test"
version := "0.1"
scalaVersion := "2.11.8"
libraryDependencies ++= Seq(
"org.scalatest" %% "scalatest" % "3.0.6" % "test")