diff --git a/dox/dev_guides/debug/debug.md b/dox/dev_guides/debug/debug.md
index 8433e2d4df..70b511e3ed 100644
--- a/dox/dev_guides/debug/debug.md
+++ b/dox/dev_guides/debug/debug.md
@@ -368,3 +368,53 @@ Each counter has its name shown when the collected statistics are printed.
 In DRAW, use command *dperf* to print all performance statistics.
 
 Note that performance counters are not thread-safe.
+
+@section occt_debug_sanitizers Use of compiler sanitizers
+
+GCC and Clang compilers provide options for instrumenting the code with the tools intended for detection of run-time errors, called sanitizers.
+This section provides some hints for using sanitizers for detecting possible errors in OCCT code.
+
+@subsection occt_debug_sanitizers_linux Linux
+
+Example of configuration steps for Ubuntu:
+
+1. In CMake configuration:
+
+  - Use up-to-date version of the GCC or CLang compiler; make sure that if CMAKE_CXX_COMPILER is set to C++ compiler (e.g. "clang++-6.0") and CMAKE_C_COMPILER is set to C compiler (e.g. "clang-6.0")
+  - Ensure that CMAKE_LINKER is set to the C++ linker bundled with compiler (e.g. clang++-6.0); this is important to avoid linking problems
+  - For building with Address sanitizer, set CMAKE_CXX_FLAGS and CMAKE_C_FLAGS to "-fsanitize=address -fno-omit-frame-pointer -fno-optimize-sibling-calls"
+  - For building with Undefined Behavior sanitizer, set CMAKE_CXX_FLAGS and CMAKE_C_FLAGS to "-fsanitize=undefined -fno-omit-frame-pointer -fno-optimize-sibling-calls"
+  - Set CMAKE_BUILD_TYPE to RelWithDebInfo to get more informative stack traces on errors
+
+2. Build as usual (make)
+
+  Be prepared that it works much slower than normal build and consumes more disk space.
+
+3. Before running executable, make sure that "llvm-symbolizer" is in PATH; this is necessary to get human-readable stack traces. The tool must have exactly that name.
+
+  If it is installed in common folder (/usr/bin or similar) with different name, one option is to create a symlink, for instance:
+> sudo ln -s /usr/bin/llvm-symbolizer-6.0 /usr/bin/llvm-symbolizer
+
+  Alternatively, add directory where actual llvm-symbolizer is located (such as /usr/lib/llvm-6.0/bin) to the PATH variable. 
+
+4. Set environment variable to disable memory leaks detection (they seem to be reported for every global variable at exit, not much useful):
+> export ASAN_OPTIONS=detect_leaks=0
+
+5. Set environment variable CSF_CPULIMIT_FACTOR to reasonably large number to increase the time limits for program execution (used by OCCT tests) to compensate the performance penalty introduced by sanitizers:
+> export CSF_CPULIMIT_FACTOR=20
+
+6. When using UBSan, set environment variable UBSAN_OPTIONS to get stack traces:
+> export UBSAN_OPTIONS=print_stacktrace=1
+
+7. Run DRAW and perform tests as usual, keeping in mind that running with sanitizer is much heavier than normal build:
+> ./draw.sh relwithdeb  <br>
+> Draw[]> testgrid -parallel 0
+
+Note that when running tests under sanitizers, behavior may be different.
+Known problems (as of CLang 6.0) are:
+- Software signals (access violation etc.) are not handled
+- Heap memory usage always reports zero
+
+@subsection occt_debug_sanitizers_windows Windows
+
+Though CLang toolset is available in Visual Studio 2015 and newer, sanitizer do not seem to be available out of the box (last tested with VS 2019 16.2.3).
diff --git a/src/Draw/Draw_BasicCommands.cxx b/src/Draw/Draw_BasicCommands.cxx
index 4b5e06007b..b469a0668c 100644
--- a/src/Draw/Draw_BasicCommands.cxx
+++ b/src/Draw/Draw_BasicCommands.cxx
@@ -537,13 +537,24 @@ static void *CpuFunc(void* /*threadarg*/)
 }
 #endif
 
-#ifdef _WIN32
-static Standard_Integer cpulimit(Draw_Interpretor&, Standard_Integer n, const char** a)
+// Returns time in seconds defined by the argument string,
+// multiplied by factor defined in environment variable
+// CSF_CPULIMIT_FACTOR (if it exists, 1 otherwise)
+static clock_t GetCpuLimit (const Standard_CString theParam)
 {
-#else
+  clock_t aValue = Draw::Atoi (theParam);
+
+  OSD_Environment aEnv("CSF_CPULIMIT_FACTOR");
+  TCollection_AsciiString aEnvStr = aEnv.Value();
+  if (!aEnvStr.IsEmpty())
+  {
+    aValue *= Draw::Atoi (aEnvStr.ToCString());
+  }
+  return aValue;
+}
+
 static Standard_Integer cpulimit(Draw_Interpretor& di, Standard_Integer n, const char** a)
 {
-#endif
   static int aFirst = 1;
 #ifdef _WIN32
   // Windows specific code
@@ -553,7 +564,7 @@ static Standard_Integer cpulimit(Draw_Interpretor& di, Standard_Integer n, const
   if (n <= 1){
     CPU_LIMIT = RLIM_INFINITY;
   } else {
-    CPU_LIMIT = Draw::Atoi (a[1]);
+    CPU_LIMIT = GetCpuLimit (a[1]);
     Standard_Real anUserSeconds, aSystemSeconds;
     OSD_Chronometer::GetProcessCPU (anUserSeconds, aSystemSeconds);
     CPU_CURRENT = clock_t(anUserSeconds + aSystemSeconds);
@@ -573,7 +584,7 @@ static Standard_Integer cpulimit(Draw_Interpretor& di, Standard_Integer n, const
   if (n <= 1)
     rlp.rlim_cur = RLIM_INFINITY;
   else
-    rlp.rlim_cur = Draw::Atoi(a[1]);
+    rlp.rlim_cur = GetCpuLimit (a[1]);
   CPU_LIMIT = rlp.rlim_cur;
 
   int status;
@@ -597,10 +608,10 @@ static Standard_Integer cpulimit(Draw_Interpretor& di, Standard_Integer n, const
     pthread_create(&cpulimitThread, NULL, CpuFunc, NULL);
   }
 #endif
+  di << "CPU and elapsed time limit set to " << (double)CPU_LIMIT << " seconds";
   return 0;
 }
 
-
 //=======================================================================
 //function : mallochook
 //purpose  : 
diff --git a/src/DrawResources/TestCommands.tcl b/src/DrawResources/TestCommands.tcl
index 5363fabe84..ec5acf5f98 100644
--- a/src/DrawResources/TestCommands.tcl
+++ b/src/DrawResources/TestCommands.tcl
@@ -144,7 +144,9 @@ help testgrid {
   -xml filename: write XML report for Jenkins (in JUnit-like format)
   -beep: play sound signal at the end of the tests
   -regress dirname: re-run only a set of tests that have been detected as regressions on some previous run.
+  -skipped dirname: re-run only a set of tests that have been skipped on some previous run.
                     Here "dirname" is path to directory containing results of previous run.
+  -skip N: skip first N tests (useful to restart after abort)
   Groups, grids, and test cases to be executed can be specified by list of file 
   masks, separated by spaces or comma; default is all (*).
 }
@@ -172,7 +174,10 @@ proc testgrid {args} {
     set exc_grid 0
     set exc_case 0
     set regress 0
-    set prev_logdir ""
+    set skipped 0
+    set logdir_regr ""
+    set logdir_skip ""
+    set nbskip 0
     for {set narg 0} {$narg < [llength $args]} {incr narg} {
         set arg [lindex $args $narg]
 
@@ -234,13 +239,29 @@ proc testgrid {args} {
         }
 
         # re-run only a set of tests that have been detected as regressions on some previous run
-        if { $arg == "-regress" } {
+        if { $arg == "-regress" || $arg == "-skipped" } {
             incr narg
             if { $narg < [llength $args] && ! [regexp {^-} [lindex $args $narg]] } {
-                set prev_logdir [lindex $args $narg]
-                set regress 1
+                if { $arg == "-regress" } {
+                    set logdir_regr [file normalize [string trim [lindex $args $narg]]]
+                    set regress 1
+                } else {
+                    set logdir_skip [file normalize [string trim [lindex $args $narg]]]
+                    set skipped 1
+                }
             } else {
-                error "Option -regress requires argument"
+                error "Option $arg requires argument"
+            }
+            continue
+        }
+
+        # skip N first tests
+        if { $arg == "-skip" } {
+            incr narg
+            if { $narg < [llength $args] && [string is integer [lindex $args $narg]] } { 
+                set nbskip [lindex $args $narg]
+            } else {
+                error "Option -skip requires integer argument"
             }
             continue
         }
@@ -303,7 +324,6 @@ proc testgrid {args} {
 
     # check that target log directory is empty or does not exist
     set logdir [file normalize [string trim $logdir]]
-    set prev_logdir [file normalize [string trim $prev_logdir]]
     if { $logdir == "" } {
         # if specified logdir is empty string, generate unique name like 
         # results/<branch>_<timestamp>
@@ -332,7 +352,7 @@ proc testgrid {args} {
     # if option "regress" is given
     set rerun_group_grid_case {}
 
-    if { ${regress} > 0 } {
+    if { ${regress} > 0 || ${skipped} > 0 } {
         if { "${groupmask}" != "*"} {
             lappend rerun_group_grid_case [list $groupmask $gridmask $casemask]
         }
@@ -341,8 +361,8 @@ proc testgrid {args} {
     }
 
     if { ${regress} > 0 } {
-        if { [file exists ${prev_logdir}/tests.log] } {
-            set fd [open ${prev_logdir}/tests.log]
+        if { [file exists ${logdir_regr}/tests.log] } {
+            set fd [open ${logdir_regr}/tests.log]
             while { [gets $fd line] >= 0 } {
                 if {[regexp {CASE ([^\s]+) ([^\s]+) ([^\s]+): FAILED} $line dump group grid casename] ||
                     [regexp {CASE ([^\s]+) ([^\s]+) ([^\s]+): IMPROVEMENT} $line dump group grid casename]} {
@@ -351,7 +371,20 @@ proc testgrid {args} {
             }
             close $fd
         } else {
-            error "Error: file ${prev_logdir}/tests.log is not found, check your input arguments!"
+            error "Error: file ${logdir_regr}/tests.log is not found, check your input arguments!"
+        }
+    }
+    if { ${skipped} > 0 } {
+        if { [file exists ${logdir_skip}/tests.log] } {
+            set fd [open ${logdir_skip}/tests.log]
+            while { [gets $fd line] >= 0 } {
+                if {[regexp {CASE ([^\s]+) ([^\s]+) ([^\s]+): SKIPPED} $line dump group grid casename] } {
+                    lappend rerun_group_grid_case [list $group $grid $casename]
+                }
+            }
+            close $fd
+        } else {
+            error "Error: file ${logdir_skip}/tests.log is not found, check your input arguments!"
         }
     }
 
@@ -501,7 +534,11 @@ proc testgrid {args} {
                             continue
                         }
 
-                        lappend tests_list [list $dir $group $grid $casename $casefile]
+                        if { $nbskip > 0 } {
+                            incr nbskip -1
+                        } else {
+                            lappend tests_list [list $dir $group $grid $casename $casefile]
+                        }
                     }
                 }
             }
@@ -571,7 +608,8 @@ proc testgrid {args} {
         if { $logdir != "" } { set imgdir_cmd "set imagedir $logdir/$group/$grid" }
 
         # prepare command file for running test case in separate instance of DRAW
-        set fd_cmd [open $logdir/$group/$grid/${casename}.tcl w]
+        set file_cmd "$logdir/$group/$grid/${casename}.tcl"
+        set fd_cmd [open $file_cmd w]
         puts $fd_cmd "$imgdir_cmd"
         puts $fd_cmd "set test_image $casename"
         puts $fd_cmd "_run_test $dir $group $grid $casefile t"
@@ -594,7 +632,7 @@ proc testgrid {args} {
         # commant to run DRAW with a command file;
         # note that empty string is passed as standard input to avoid possible 
         # hang-ups due to waiting for stdin of the launching process
-        set command "exec <<{} DRAWEXE -f $logdir/$group/$grid/${casename}.tcl"
+        set command "exec <<{} DRAWEXE -f $file_cmd"
 
         # alternative method to run without temporary file; disabled as it needs too many backslashes
         # else {
@@ -1558,6 +1596,7 @@ proc _log_and_puts {logvar message} {
 proc _log_test_case {output logdir dir group grid casename logvar} {
     upvar $logvar log
     set show_errors 0
+
     # check result and make HTML log
     _check_log $dir $group $grid $casename $show_errors $output summary html_log
     lappend log $summary
@@ -1567,6 +1606,11 @@ proc _log_test_case {output logdir dir group grid casename logvar} {
         _log_html $logdir/$group/$grid/$casename.html $html_log "Test $group $grid $casename"
         _log_save $logdir/$group/$grid/$casename.log "$output\n$summary" "Test $group $grid $casename"
     }
+
+    # remove intermediate command file used to run test
+    if { [file exists $logdir/$group/$grid/${casename}.tcl] } {
+        file delete $logdir/$group/$grid/${casename}.tcl
+    }
 }
 
 # Auxiliary procedure to save log to file
@@ -1710,8 +1754,8 @@ proc _log_html_summary {logdir log totals regressions improvements skipped total
     puts $fd "</table>"
 
     # time stamp and elapsed time info
+    puts $fd "<p>Generated on [clock format [clock seconds] -format {%Y-%m-%d %H:%M:%S}] on [info hostname]\n<p>"
     if { $total_time != "" } { 
-        puts $fd "<p>Generated on [clock format [clock seconds] -format {%Y-%m-%d %H:%M:%S}] on [info hostname]\n<p>"
         puts $fd [join [split $total_time "\n"] "<p>"]
     } else {
         puts $fd "<p>NOTE: This is intermediate summary; the tests are still running! This page will refresh automatically until tests are finished."
diff --git a/tests/demo/begin b/tests/demo/begin
deleted file mode 100755
index d664818133..0000000000
--- a/tests/demo/begin
+++ /dev/null
@@ -1 +0,0 @@
-# File : begin