PS> '{
    // A Json comment
    "string": "test"
}' | Test-Json
True

PS> '{
    // A Json comment
    "string": "test"
}' | Test-Json

Test-Json: Cannot parse the JSON

Exception             : 
    Type           : System.Exception
    Message        : Cannot parse the JSON.
    InnerException : 
        Type               : System.Text.Json.JsonReaderException
        LineNumber         : 1
        BytePositionInLine : 4
        Message            : '/' is invalid after a value. Expected either ',', '}', or ']'. LineNumber: 1 | BytePositionInLine: 4.
        TargetSite         : 
            Name          : ThrowJsonReaderException
            DeclaringType : System.Text.Json.ThrowHelper, System.Text.Json, Version=8.0.0.0, Culture=neutral, PublicKeyToken=cc7b13ffcd2ddd51
            MemberType    : Method
            Module        : System.Text.Json.dll
        Source             : System.Text.Json
        HResult            : -2146233088
        StackTrace         : 
   at System.Text.Json.ThrowHelper.ThrowJsonReaderException(Utf8JsonReader& json, ExceptionResource resource, Byte nextByte, ReadOnlySpan`1 bytes)
   at System.Text.Json.Utf8JsonReader.ConsumeNextToken(Byte marker)
   at System.Text.Json.Utf8JsonReader.ConsumeNextTokenOrRollback(Byte marker)
   at System.Text.Json.Utf8JsonReader.ReadSingleSegment()
   at System.Text.Json.Utf8JsonReader.Read()
   at System.Text.Json.JsonDocument.Parse(ReadOnlySpan`1 utf8JsonSpan, JsonReaderOptions readerOptions, MetadataDb& database, StackRowStack& stack)
   at System.Text.Json.JsonDocument.ParseUnrented(ReadOnlyMemory`1 utf8Json, JsonReaderOptions readerOptions, JsonTokenType tokenType)
   at System.Text.Json.JsonDocument.ParseValue(ReadOnlyMemory`1 json, JsonDocumentOptions options)
   at System.Text.Json.Nodes.JsonNode.Parse(String json, Nullable`1 nodeOptions, JsonDocumentOptions documentOptions)
   at Microsoft.PowerShell.Commands.TestJsonCommand.ProcessRecord()
    HResult        : -2146233088
TargetObject          : {
    // A Json comment
    "string": "test"
}
CategoryInfo          : InvalidData: ({
    // A Json com… "string": "test"
}:String) [Test-Json], Exception
FullyQualifiedErrorId : InvalidJson,Microsoft.PowerShell.Commands.TestJsonCommand
InvocationInfo        : 
    MyCommand        : Test-Json
    ScriptLineNumber : 4
    OffsetInLine     : 6
    HistoryId        : 4
    Line             : }' | Test-Json
    Statement        : Test-Json
    PositionMessage  : At line:4 char:6
                       + }' | Test-Json
                       +      ~~~~~~~~~
    InvocationName   : Test-Json
    CommandOrigin    : Internal
ScriptStackTrace      : at <ScriptBlock>, <No file>: line 1
PipelineIterationInfo :