diff --git a/README.md b/README.md
index 87f1efb..7af9bc6 100644
--- a/README.md
+++ b/README.md
@@ -1 +1 @@
-Document structure for editor
\ No newline at end of file
+Manage a document's content as a sequence of lines.
\ No newline at end of file
diff --git a/src/doci.xqm b/src/doci.xqm
index f0c7f12..74cc943 100644
--- a/src/doci.xqm
+++ b/src/doci.xqm
@@ -66,9 +66,10 @@ declare function doci:text($doci as doci:doci)
 as xs:string{
   string-join($doci?lines,$doci?separator)
 };
+
 (: number of lines:)
 declare function doci:lines($doci as doci:doci)
-as xs:string{
+as xs:integer{
   $doci?lines=>count()
 };
 
@@ -82,30 +83,39 @@ switch () {
   default return $doci:default-separator
 }
 };
+
 (: apply change:)
-declare function doci:change($doci as doci:doci,$change as doci:TextDocumentContentChangeEvent)
+declare function doci:update($doci as doci:doci,$change as doci:TextDocumentContentChangeEvent)
 as doci:doci{
-    let $lines:= doci:split-lines($change?text)
-    return if(empty($change?range))
-           then doci:doci($lines,$doci?separator)
-           else let $range:=$change?range
-                let $sline:=$range?start?line
-                let $eline:=$range?end?line
-                return switch(){
-                  case $sline eq $eline and count($lines) eq 1
-                  return let $line:=$doci?lines[$sline+1]
-                         let $new:=substring($line,1,$range?start?character)
-                                   || $lines ||
-                                   substring($line,1+$range?end?character)
+let $lines:= doci:split-lines($change?text)
+return  if(empty($change?range))
+        then doci:doci($lines,$doci?separator)
+        else 
+              let $range:=$change?range
+              let $sline:= $range?start?line
+              let $eline:= $range?end?line
 
-                          let $ulines:=( $doci?lines[position() le $sline],
-                                    $new,
-                                    $doci?lines[position() gt 1+$sline]
-                                    )
-                          return doci:doci($ulines, $doci?separator)
+              (: string from start line before insert  :)
+              let $head:= substring( $doci?lines[$sline+1] ,1, $range?start?character )
+              (: string from edit end to end of line :)
+              let $head:= substring( $doci?lines[$sline+1] ,1, $range?start?character )                                                 
+              let $last := substring( $doci?lines[$eline+1] , $range?end?character +1)
 
-                  default return error(#doci:change,"oh")
-                }
+let $ulines := (
+            subsequence($doci?lines, 1, $sline) (: lines before edit :)
+            ,
+            if($sline eq $eline)
+            then ($head || $lines[1] || $last) 
+            
+            else (
+                   $head || $lines[1],
+                   subsequence( $lines,2, count( $lines - 2)),
+                   $lines[last()] ||$last
+                 ),
+           
+             subsequence($doci?lines, $eline+2) (: lines after edit :)
+             )   
+return doci:doci($ulines,$doci?separator)
 };
 
 declare function doci:split-lines($text as xs:string)
diff --git a/test/doci.xq b/test/doci.xq
deleted file mode 100644
index 64eb4fd..0000000
--- a/test/doci.xq
+++ /dev/null
@@ -1,10 +0,0 @@
-import module namespace doci = 'urn:doci' at "../src/doci.xqm";
-
-declare variable $long:=
-file:read-text("C:\Users\mrwhe\git\quodatum\basex-lsp\test\sample.docs\pdfbox.xqm");
-declare variable $text:=`ABV
-ddddd
-`;
-
-
-doci:build($long)?length
\ No newline at end of file
diff --git a/test/simple.xqm b/test/simple.xqm
index 9c4cf1d..7cee11f 100644
--- a/test/simple.xqm
+++ b/test/simple.xqm
@@ -2,11 +2,12 @@
 module namespace test = 'test:doci';
 import module namespace doci = 'urn:doci' at "../src/doci.xqm";
 
+
 (:~ we can create record from file :)
 declare %unit:test function test:from-file() {
   let $doc:=test:read("resources/doc1.txt")
   let $doci:= doci:build($doc)
-  return test:expected($doc,$doci,530)
+  return test:expected($doci,$doc,530)
    
 };
 
@@ -14,7 +15,7 @@ declare %unit:test function test:from-file() {
 declare %unit:test function test:from-string1() {
   let $doc:="a one line string"
   let $doci:= doci:build($doc)
-  return test:expected($doc,$doci,1)
+  return test:expected($doci, $doc, 1)
     
 };
 (:~ we can create record from string :)
@@ -22,39 +23,43 @@ declare %unit:test function test:from-string2() {
   let $doc:="a two line string
 second line"
   let $doci:= doci:build($doc)
-  return test:expected($doc,$doci,2)
+  return test:expected($doci,$doc,2)
     
 };
 (:~ we can create update from string :)
-declare %unit:test function test:update1() {
+declare %unit:test function test:update-start() {
   let $doc:="123456789"
   let $doci:= doci:build($doc)
-  let $change:=test:change("*",0,0,0,0)
-  let $doci2:=doci:change($doci,$change)=>trace("A")
+  let $_:= test:expected($doci,$doc,1)
+  
+  let $change:=test:def-change("*",0,0,0,0)
+  let $doci2:=doci:update($doci,$change)=>trace("US1")
+  let $_:= test:expected($doci2,"*" || $doc,1)
 
-  let $change2:=test:change("",0,0,0,1)
-  let $update:=doci:change($doci2,$change2)=>trace("b")            
+  let $change2:=test:def-change("",0,0,0,1)
+  let $update:=doci:update($doci2,$change2)=>trace("b")
+  let $_:= doci:text($update)=>trace("test:update1")            
   return ()  
 };
 
 (:~ we can create update from string :)
-declare %unit:test function test:update2() {
+declare %unit:test  function test:update-end() {
   let $doc:="a
 123456789
 b"
   let $doci:= doci:build($doc)
-  let $_:=test:expected($doc,$doci,3)
-  let $change:=test:change("*",1,9,1,9)
-  let $doci2:=doci:change($doci,$change)=>trace("A")
+  let $_:=test:expected($doci,$doc,3)
+  let $change:=test:def-change("*",1,9,1,9)
+  let $doci2:=doci:update($doci,$change)
 
-  let $change2:=test:change("",1,9,1,10)
-  let $update:=doci:change($doci2,$change2)=>trace("b")            
-  return ()  
+  let $change2:=test:def-change("",1,9,1,10)
+  let $update:=doci:update($doci2,$change2)           
+  return unit:assert-equals($doc,doci:text($update))
 };
 
 (: test $doci properties as expected :)
-declare function test:expected($doc as xs:string, $doci as doci:doci, $lines as xs:integer){
-   unit:assert-equals($doci?lines=>count(),$lines),
+declare function test:expected($doci as doci:doci, $doc as xs:string,  $lines as xs:integer){
+   unit:assert-equals(doci:lines($doci),$lines),
    unit:assert($doci?separator!string-length(.)>0),
    unit:assert-equals($doc,doci:text($doci))
 };
@@ -72,7 +77,7 @@ file:resolve-path($path,file:base-dir())=>file:read-text()
 };
 
 (: create a change description:)
-declare function test:change($text as xs:string,
+declare function test:def-change($text as xs:string,
                              $sline as xs:integer,$schar as xs:integer,
                              $eline as xs:integer,$echar as xs:integer
                              )
diff --git a/test/smoke.xq b/test/smoke.xq
new file mode 100644
index 0000000..a3a918b
--- /dev/null
+++ b/test/smoke.xq
@@ -0,0 +1,22 @@
+import module namespace doci = 'urn:doci' at "../src/doci.xqm";
+
+declare variable $long:=
+file:read-text("C:\Users\mrwhe\git\quodatum\basex-lsp\test\sample.docs\pdfbox.xqm");
+declare variable $text:="123456789";
+
+(: create a change description:)
+declare function local:change($text as xs:string,
+                             $sline as xs:integer,$schar as xs:integer,
+                             $eline as xs:integer,$echar as xs:integer
+                             )
+as doci:TextDocumentContentChangeEvent{
+doci:TextDocumentContentChangeEvent(
+            $text,
+            doci:Range(doci:Position($sline,$schar),doci:Position($eline,$echar))
+            )
+};
+
+
+
+doci:build($text)
+=>doci:change(local:change("*",0,0,0,0))
\ No newline at end of file