diff --git a/DESCRIPTION b/DESCRIPTION
index 0b86cd5..c8ecbf6 100644
--- a/DESCRIPTION
+++ b/DESCRIPTION
@@ -11,6 +11,7 @@ Authors@R: c(person(given = "Christian",
 Depends: R (>= 3.6),
   IRanges,
 	methods,
+	S4Vectors,
 	Spectra,
 	rDotNet (>= 0.9)
 Suggests:
diff --git a/NAMESPACE b/NAMESPACE
index eea11ca..e5ae2d9 100644
--- a/NAMESPACE
+++ b/NAMESPACE
@@ -3,6 +3,7 @@
 export(MsBackendRawFileReader)
 importClassesFrom(Spectra,MsBackendDataFrame)
 importFrom(IRanges,NumericList)
+importFrom(S4Vectors,DataFrame)
 importFrom(methods,callNextMethod)
 importFrom(methods,new)
 importFrom(rDotNet,.cinit)
diff --git a/R/MsBackendRawFileReader-functions.R b/R/MsBackendRawFileReader-functions.R
index 707588a..9051aba 100644
--- a/R/MsBackendRawFileReader-functions.R
+++ b/R/MsBackendRawFileReader-functions.R
@@ -18,6 +18,7 @@ MsBackendRawFileReader <- function() {
 #' adapted from the MsBackendMzR-function.R file by Johannes Rainer
 #'
 #' @return `DataFrame` with the header.
+#' @importFrom S4Vectors DataFrame
 #' @noRd
 .MsBackendRawFileReader_header <- function(x) {
     stopifnot(class(x) == "rDotNet")
@@ -27,10 +28,10 @@ MsBackendRawFileReader <- function() {
     first <- x$getFirstScanNumber()
     last <- x$getLastScanNumber()
     
-    S4Vectors::DataFrame(
+    DataFrame(
       scanIndex = first:last,
       msLevel = vapply(first:last, FUN=function(z){x$GetMsLevel(z)}, FUN.VALUE = as.integer(1)),
-      precursorMz = vapply(first:last, FUN=function(z){x$GetPepmass(z)}, FUN.VALUE = as.double(1.0)),
+      precursorMz = vapply(first:last, FUN=function(z){x$GetPrecursorMz(z)}, FUN.VALUE = as.double(1.0)),
       precursorCharge = as.integer(vapply(first:last, FUN=function(z){x$GetCharge(z)}, FUN.VALUE = as.character(1.0))),
       rtime =   vapply(first:last, FUN=function(z){x$GetRTinSeconds(z)}, FUN.VALUE = as.double(1.0))
     )
diff --git a/R/MsBackendRawFileReader.R b/R/MsBackendRawFileReader.R
index d47cf4e..8de4460 100644
--- a/R/MsBackendRawFileReader.R
+++ b/R/MsBackendRawFileReader.R
@@ -3,9 +3,9 @@ NULL
 
 
 #' @title RawFileReader-based backend
-#'
+#' @aliases MsBackendRawFileReader
 #' @description
-#'
+
 #' The `MsBackendRawFileReader` inherits all slots and methods from the base
 #' `MsBackendDataFrame` (in-memory) backend. It overrides the base `mz` and
 #' `intensity` methods as well as `peaks` to read the respective data from
@@ -23,7 +23,6 @@ NULL
 #' adapted from the MsBackendMzR.R file by Johannes Rainer
 #' 
 #' @importClassesFrom Spectra MsBackendDataFrame 
-#' @rdname hidden_aliases
 setClass("MsBackendRawFileReader",
          contains = "MsBackendDataFrame",
          prototype = prototype(version = "0.1",
diff --git a/exec/MsBackendRawFileReader.dll b/exec/MsBackendRawFileReader.dll
deleted file mode 100755
index 9beaf72..0000000
Binary files a/exec/MsBackendRawFileReader.dll and /dev/null differ
diff --git a/man/MsBackendRawFileReader-class.Rd b/man/MsBackendRawFileReader-class.Rd
new file mode 100644
index 0000000..3b53fbf
--- /dev/null
+++ b/man/MsBackendRawFileReader-class.Rd
@@ -0,0 +1,25 @@
+% Generated by roxygen2: do not edit by hand
+% Please edit documentation in R/MsBackendRawFileReader.R
+\docType{class}
+\name{MsBackendRawFileReader-class}
+\alias{MsBackendRawFileReader-class}
+\alias{MsBackendRawFileReader}
+\title{RawFileReader-based backend}
+\description{
+The `MsBackendRawFileReader` inherits all slots and methods from the base
+`MsBackendDataFrame` (in-memory) backend. It overrides the base `mz` and
+`intensity` methods as well as `peaks` to read the respective data from
+the original raw data files.
+
+The validator function has to ensure that the files provided in the
+`files` slot exist.
+
+The `backendInitialize` method reads the header data from the raw files and
+hence fills the `spectraData` slot. Note that this method could be called
+several times, e.g. also to *re-fill* `spectraData` after dropping some of
+its columns.
+}
+\author{
+Christian Panse 2019-06-15 
+adapted from the MsBackendMzR.R file by Johannes Rainer
+}
diff --git a/man/hidden_aliases.Rd b/man/hidden_aliases.Rd
new file mode 100644
index 0000000..f81be26
--- /dev/null
+++ b/man/hidden_aliases.Rd
@@ -0,0 +1,25 @@
+% Generated by roxygen2: do not edit by hand
+% Please edit documentation in R/hidden_aliases.R, R/MsBackendRawFileReader.R
+\docType{methods}
+\name{hidden_aliases}
+\alias{hidden_aliases}
+\alias{[,MsBackendDataFrame-method}
+\alias{backendInitialize,MsBackendRawFileReader-method}
+\alias{show,MsBackendRawFileReader-method}
+\alias{intensity,MsBackendRawFileReader-method}
+\alias{mz,MsBackendRawFileReader-method}
+\title{Internal page for hidden aliases}
+\usage{
+\S4method{backendInitialize}{MsBackendRawFileReader}(object, files,
+  spectraData, ..., BPPARAM = bpparam())
+
+\S4method{show}{MsBackendRawFileReader}(object)
+
+\S4method{intensity}{MsBackendRawFileReader}(object)
+
+\S4method{mz}{MsBackendRawFileReader}(object)
+}
+\description{
+For S4 methods that require a documentation entry but only clutter the index.
+}
+\keyword{internal}
diff --git a/src/MsBackendRawFileReader.cs b/src/MsBackendRawFileReader.cs
index 714873c..8d91310 100644
--- a/src/MsBackendRawFileReader.cs
+++ b/src/MsBackendRawFileReader.cs
@@ -96,9 +96,16 @@ public string GetTitle(int scanNumber)
             return s;
         }
 
-        public double GetPepmass(int scanNumber)
+        public double GetPrecursorMz(int scanNumber)
         {
+            
+            
+            var scanFilter = rawFile.GetFilterForScanNumber(scanNumber);
+            
+            if (scanFilter.MSOrder.ToString() == "Ms") return 0.0;
+            
             var scanEvent = rawFile.GetScanEventForScanNumber(scanNumber);
+            
             try
             {
                 var reaction0 = scanEvent.GetReaction(0);
@@ -110,13 +117,6 @@ public double GetPepmass(int scanNumber)
             }
         }
 
-        public double[] GetPepmasss()
-        {
-            var pepmass = new double[this.getLastScanNumber()];
-            foreach (int scan in this.scans) pepmass[scan] = GetPepmass(scan);
-            return pepmass;
-        }
-
         
         public string GetScanType(int scanNumber)
         {
diff --git a/tests/testthat.R b/tests/testthat.R
new file mode 100644
index 0000000..7feb6c4
--- /dev/null
+++ b/tests/testthat.R
@@ -0,0 +1,17 @@
+library("testthat")
+library("MsBackendRawFileReader")
+library("Spectra")
+
+sample_raw_file <- file.path(path.package(package = 'MsBackendRawFileReader'),
+                                'extdata', 'sample.raw')
+
+sample_mzXML_file <- file.path(path.package(package = 'MsBackendRawFileReader'),
+                                'extdata', 'sample.mzXML')
+
+
+sample_raw <-  backendInitialize(MsBackendRawFileReader(), files = sample_raw_file)
+sample_mzr <-  backendInitialize(MsBackendMzR(), files = sample_mzXML_file)
+
+
+
+test_check("MsBackendRawFileReader")
diff --git a/tests/testthat/test_MsBackendMzR_MsBackendRawFileReader.R b/tests/testthat/test_MsBackendMzR_MsBackendRawFileReader.R
new file mode 100644
index 0000000..b9f7b96
--- /dev/null
+++ b/tests/testthat/test_MsBackendMzR_MsBackendRawFileReader.R
@@ -0,0 +1,31 @@
+test_that("msLevel", {
+	expect_identical(msLevel(sample_raw), msLevel(sample_mzr))
+})
+
+
+test_that("rtime", {
+  expect_equal(rtime(sample_raw), rtime(sample_mzr), tolerance = 1E-4)
+})
+
+test_that("precursorMz", {
+  expect_equal(precursorMz(sample_raw), precursorMz(sample_mzr), tolerance = 1E-5)
+})
+
+test_that("precursorCharge", {
+  expect_identical(precursorCharge(sample_raw), precursorCharge(sample_mzr))
+})
+
+
+test_that("peaks", {
+  
+  sample_peaks_raw <- peaks(sample_raw)
+  sample_peaks_mzr <- peaks(sample_mzr)
+  
+  n <- length(sample_peaks_raw )
+  expect_true(n == 574)
+  
+  rv <- lapply(1:n, function(i){
+    expect_identical(sample_peaks_raw[[i]] , sample_peaks_mzr[[i]])
+  })
+  
+})