I installed from Nugget Package Specflow, Specflow.NUnit, Nunit and Nunit3TestAdapter, and I already intalled too the extension for Visual Studio for Specflow a NUnitTestAdapter, but I can't see the test in TestExplorer window, any idea?
You need to:
Install the SpecFlow.Tools.MsBuild.Generation NuGet package: https://www.nuget.org/packages/SpecFlow.Tools.MsBuild.Generation/
Install the SpecFlow extension for Visual Studio: https://marketplace.visualstudio.com/items?itemName=TechTalkSpecFlowTeam.SpecFlowForVisualStudio
Make sure Tools > SpecFlow > Legacy > Use SpecFlowSingleFileGenerator Custom Tool is False
Right click on each feature file and make sure Custom Tool is blank. It used to be SpecFlowSingleFileGenerator in SpecFlow 2.x.
More info: Generating code behind files using MS Build.