Using VS Code, Coverlet, xUnit, plus these extensions

Image of it all together

Note the tasks.json, specifically this part. If you name the file lcov.info, the Coverage Gutters extension will pick up and color the line numbers.

        {
            "label": "test with coverage",
            "command": "dotnet",
            "type": "process",
            "args": [
                "test",
                "/p:CollectCoverage=true",
                "/p:CoverletOutputFormat=lcov",
                "/p:CoverletOutput=./lcov.info",
                "${workspaceFolder}/The.Tests/The.Tests.csproj"
            ],
            "problemMatcher": "$msCompile",
            "group": {
                "kind": "test",
                "isDefault": true
            }
        },