Index: Makefile.in
==================================================================
--- Makefile.in
+++ Makefile.in
@@ -420,10 +420,11 @@
   $(TOP)/src/test_superlock.c \
   $(TOP)/src/test_syscall.c \
   $(TOP)/src/test_tclsh.c \
   $(TOP)/src/test_tclvar.c \
   $(TOP)/src/test_thread.c \
+  $(TOP)/src/test_vdbecov.c \
   $(TOP)/src/test_vfs.c \
   $(TOP)/src/test_windirent.c \
   $(TOP)/src/test_window.c \
   $(TOP)/src/test_wsd.c       \
   $(TOP)/ext/fts3/fts3_term.c \

Index: Makefile.msc
==================================================================
--- Makefile.msc
+++ Makefile.msc
@@ -1515,10 +1515,11 @@
   $(TOP)\src\test_superlock.c \
   $(TOP)\src\test_syscall.c \
   $(TOP)\src\test_tclsh.c \
   $(TOP)\src\test_tclvar.c \
   $(TOP)\src\test_thread.c \
+  $(TOP)\src\test_vdbecov.c \
   $(TOP)\src\test_vfs.c \
   $(TOP)\src\test_windirent.c \
   $(TOP)\src\test_window.c \
   $(TOP)\src\test_wsd.c \
   $(TOP)\ext\fts3\fts3_term.c \

Index: main.mk
==================================================================
--- main.mk
+++ main.mk
@@ -346,10 +346,11 @@
   $(TOP)/src/test_superlock.c \
   $(TOP)/src/test_syscall.c \
   $(TOP)/src/test_tclsh.c \
   $(TOP)/src/test_tclvar.c \
   $(TOP)/src/test_thread.c \
+  $(TOP)/src/test_vdbecov.c \
   $(TOP)/src/test_vfs.c \
   $(TOP)/src/test_windirent.c \
   $(TOP)/src/test_window.c \
   $(TOP)/src/test_wsd.c
 

Index: src/test_tclsh.c
==================================================================
--- src/test_tclsh.c
+++ src/test_tclsh.c
@@ -104,10 +104,11 @@
 #ifdef SQLITE_ENABLE_ZIPVFS
   extern int Zipvfs_Init(Tcl_Interp*);
 #endif
   extern int TestExpert_Init(Tcl_Interp*);
   extern int Sqlitetest_window_Init(Tcl_Interp *);
+  extern int Sqlitetestvdbecov_Init(Tcl_Interp *);
 
   Tcl_CmdInfo cmdInfo;
 
   /* Since the primary use case for this binary is testing of SQLite,
   ** be sure to generate core files if we crash */
@@ -169,10 +170,11 @@
 #if defined(SQLITE_ENABLE_FTS3) || defined(SQLITE_ENABLE_FTS4)
   Sqlitetestfts3_Init(interp);
 #endif
   TestExpert_Init(interp);
   Sqlitetest_window_Init(interp);
+  Sqlitetestvdbecov_Init(interp);
 
   Tcl_CreateObjCommand(
       interp, "load_testfixture_extensions", load_testfixture_extensions,0,0
   );
   return 0;

ADDED   src/test_vdbecov.c
Index: src/test_vdbecov.c
==================================================================
--- src/test_vdbecov.c
+++ src/test_vdbecov.c
@@ -0,0 +1,107 @@
+/*
+** 2019 April 02
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+******************************************************************************
+**
+*/
+#if SQLITE_TEST          /* This file is used for testing only */
+
+#include "sqlite3.h"
+#include "sqliteInt.h"
+#if defined(INCLUDE_SQLITE_TCL_H)
+#  include "sqlite_tcl.h"
+#else
+#  include "tcl.h"
+#endif
+
+#ifdef SQLITE_VDBE_COVERAGE
+
+static u8 aBranchArray[200000];
+
+static void test_vdbe_branch(
+  void *pCtx, 
+  unsigned int iSrc, 
+  unsigned char iBranch, 
+  unsigned char iType
+){
+  if( iSrc<sizeof(aBranchArray) ){
+    aBranchArray[iSrc] |= iBranch;
+  }
+}
+
+static void appendToList(Tcl_Obj *pList, int iLine, int iPath){
+  Tcl_Obj *pNew = Tcl_NewObj();
+  Tcl_IncrRefCount(pNew);
+  Tcl_ListObjAppendElement(0, pNew, Tcl_NewIntObj(iLine));
+  Tcl_ListObjAppendElement(0, pNew, Tcl_NewIntObj(iPath));
+  Tcl_ListObjAppendElement(0, pList, pNew);
+  Tcl_DecrRefCount(pNew);
+}
+
+
+static int SQLITE_TCLAPI test_vdbe_coverage(
+  ClientData cd,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  const char *aSub[] = { "start", "report", "stop", 0 };
+  int iSub = -1;
+  if( objc!=2 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "sub-command");
+    return TCL_ERROR;
+  }
+
+  if( Tcl_GetIndexFromObj(interp, objv[1], aSub, "sub-command", 0, &iSub) ){
+    return TCL_ERROR;
+  }
+
+  Tcl_ResetResult(interp);
+  assert( iSub==0 || iSub==1 || iSub==2 );
+  switch( iSub ){
+    case 0:       /* start */
+      memset(aBranchArray, 0, sizeof(aBranchArray));
+      sqlite3_test_control(SQLITE_TESTCTRL_VDBE_COVERAGE, test_vdbe_branch, 0);
+      break;
+    case 1: {     /* report */
+      int i;
+      Tcl_Obj *pRes = Tcl_NewObj();
+      Tcl_IncrRefCount(pRes);
+      for(i=0; i<sizeof(aBranchArray); i++){
+        u8 b = aBranchArray[i];
+        if( b ){
+          if( (b & 0x01)==0 ) appendToList(pRes, i, 0);
+          if( (b & 0x02)==0 ) appendToList(pRes, i, 1);
+          if( (b & 0x04)==0 ) appendToList(pRes, i, 2);
+        }
+      }
+      Tcl_SetObjResult(interp, pRes);
+      Tcl_DecrRefCount(pRes);
+      break;
+    };
+      
+    default:      /* stop */         
+      sqlite3_test_control(SQLITE_TESTCTRL_VDBE_COVERAGE, 0, 0);
+      break;
+  }
+
+  return TCL_OK;
+}
+
+#endif  /* SQLITE_VDBE_COVERAGE */
+
+int Sqlitetestvdbecov_Init(Tcl_Interp *interp){
+#ifdef SQLITE_VDBE_COVERAGE
+  Tcl_CreateObjCommand(interp, "vdbe_coverage", test_vdbe_coverage, 0, 0);
+#endif
+  return TCL_OK;
+}
+
+#endif

Index: test/tester.tcl
==================================================================
--- test/tester.tcl
+++ test/tester.tcl
@@ -574,10 +574,14 @@
   }
 
   if {$cmdlinearg(verbose)==""} {
     set cmdlinearg(verbose) 1
   }
+
+  if {[info commands vdbe_coverage]!=""} {
+    vdbe_coverage start
+  }
 }
 
 # Update the soft-heap-limit each time this script is run. In that
 # way if an individual test file changes the soft-heap-limit, it
 # will be reset at the start of the next test file.
@@ -1293,19 +1297,55 @@
     if {[sqlite3_memory_used]>0} {
       output2 "Writing leaks.tcl..."
       sqlite3_memdebug_log sync
       memdebug_log_sql leaks.tcl
     }
+  }
+  if {[info commands vdbe_coverage]!=""} {
+    vdbe_coverage_report
   }
   foreach f [glob -nocomplain test.db-*-journal] {
     forcedelete $f
   }
   foreach f [glob -nocomplain test.db-mj*] {
     forcedelete $f
   }
   exit [expr {$nErr>0}]
 }
+
+proc vdbe_coverage_report {} {
+  puts "Writing vdbe coverage report to vdbe_coverage.txt"
+  set lSrc [list]
+  set iLine 0
+  if {[file exists ../sqlite3.c]} {
+    set fd [open ../sqlite3.c]
+    set iLine
+    while { ![eof $fd] } {
+      set line [gets $fd]
+      incr iLine
+      if {[regexp {^/\** Begin file (.*\.c) \**/} $line -> file]} {
+        lappend lSrc [list $iLine $file]
+      }
+    }
+    close $fd
+  }
+  set fd [open vdbe_coverage.txt w]
+  foreach miss [vdbe_coverage report] {
+    foreach {line branch} $miss {}
+    set nextfile ""
+    while {[llength $lSrc]>0 && [lindex $lSrc 0 0] < $line} {
+      set nextfile [lindex $lSrc 0 1]
+      set lSrc [lrange $lSrc 1 end]
+    }
+    if {$nextfile != ""} {
+      puts $fd ""
+      puts $fd "### $nextfile ###"
+    }
+    puts $fd "Vdbe branch $line: path $branch never taken"
+  }
+  close $fd
+}
 
 # Display memory statistics for analysis and debugging purposes.
 #
 proc show_memstats {} {
   set x [sqlite3_status SQLITE_STATUS_MEMORY_USED 0]

Index: test/windowerr.tcl
==================================================================
--- test/windowerr.tcl
+++ test/windowerr.tcl
@@ -52,9 +52,18 @@
 }
 
 errorsql_test 2.2 {
   SELECT sum(a) OVER () AS xyz FROM t1 ORDER BY sum(xyz);
 }
+
+errorsql_test 3.0 {
+  SELECT sum(a) OVER win FROM t1
+  WINDOW win AS (ROWS BETWEEN 'hello' PRECEDING AND 10 FOLLOWING)
+}
+errorsql_test 3.2 {
+  SELECT sum(a) OVER win FROM t1
+  WINDOW win AS (ROWS BETWEEN 10 PRECEDING AND x'ABCD' FOLLOWING)
+}
 
 
 finish_test
 

Index: test/windowerr.test
==================================================================
--- test/windowerr.test
+++ test/windowerr.test
@@ -93,7 +93,19 @@
 
 # PG says ERROR:  column "xyz" does not exist
 do_test 2.2 { catch { execsql {
   SELECT sum(a) OVER () AS xyz FROM t1 ORDER BY sum(xyz);
 } } } 1
+
+# PG says ERROR:  invalid input syntax for integer: "hello"
+do_test 3.0 { catch { execsql {
+  SELECT sum(a) OVER win FROM t1
+  WINDOW win AS (ROWS BETWEEN 'hello' PRECEDING AND 10 FOLLOWING)
+} } } 1
+
+# PG says ERROR:  argument of ROWS must be type bigint, not type bit
+do_test 3.2 { catch { execsql {
+  SELECT sum(a) OVER win FROM t1
+  WINDOW win AS (ROWS BETWEEN 10 PRECEDING AND x'ABCD' FOLLOWING)
+} } } 1
 
 finish_test