diff --git a/Lib/test/test_trace.py b/Lib/test/test_trace.py
index 247c49c..8ca9ba4 100644
--- a/Lib/test/test_trace.py
+++ b/Lib/test/test_trace.py
@@ -1,10 +1,286 @@
-# Testing the trace module
-
-from test.support import run_unittest, TESTFN, rmtree, unlink, captured_stdout
+import os
+import sys
+from test.support import (run_unittest, TESTFN, rmtree, unlink,
+                               captured_stdout)
 import unittest
-import trace
-import os, sys
 
+import trace
+from trace import CoverageResults, Trace
+
+from test.tracedmodules import testmod
+
+
+#------------------------------- Utilities -----------------------------------#
+
+def fix_ext_py(filename):
+    """Given a .pyc/.pyo filename converts it to the appropriate .py"""
+    if filename.endswith(('.pyc', '.pyo')):
+        filename = filename[:-1]
+    return filename
+
+def my_file_and_modname():
+    """The .py file and module name of this file (__file__)"""
+    modname = os.path.splitext(os.path.basename(__file__))[0]
+    return fix_ext_py(__file__), modname
+
+def get_firstlineno(func):
+    return func.__code__.co_firstlineno
+
+#-------------------- Target functions for tracing ---------------------------#
+#
+# The relative line numbers of lines in these functions matter for verifying
+# tracing. Please modify the appropriate tests if you change one of the
+# functions. Absolute line numbers don't matter.
+#
+
+def traced_func_linear(x, y):
+    a = x
+    b = y
+    c = a + b
+    return c
+
+def traced_func_loop(x, y):
+    c = x
+    for i in range(5):
+        c += y
+    return c
+
+def traced_func_importing(x, y):
+    return x + y + testmod.func(1)
+
+def traced_func_simple_caller(x):
+    c = traced_func_linear(x, x)
+    return c + x
+
+def traced_func_importing_caller(x):
+    k = traced_func_simple_caller(x)
+    k += traced_func_importing(k, x)
+    return k
+
+def traced_func_generator(num):
+    c = 5       # executed once
+    for i in range(num):
+        yield i + c
+
+def traced_func_calling_generator():
+    k = 0
+    for i in traced_func_generator(10):
+        k += i
+
+def traced_doubler(num):
+    return num * 2
+
+def traced_caller_list_comprehension():
+    k = 10
+    mylist = [traced_doubler(i) for i in range(k)]
+    return mylist
+
+
+class TracedClass(object):
+    def __init__(self, x):
+        self.a = x
+
+    def inst_method_linear(self, y):
+        return self.a + y
+
+    def inst_method_calling(self, x):
+        c = self.inst_method_linear(x)
+        return c + traced_func_linear(x, c)
+
+    @classmethod
+    def class_method_linear(cls, y):
+        return y * 2
+
+    @staticmethod
+    def static_method_linear(y):
+        return y * 2
+
+
+#------------------------------ Test cases -----------------------------------#
+
+
+class TestLineCounts(unittest.TestCase):
+    """White-box testing of line-counting, via runfunc"""
+    def setUp(self):
+        self.tracer = Trace(count=1, trace=0, countfuncs=0, countcallers=0)
+        self.my_py_filename = fix_ext_py(__file__)
+        self.maxDiff = None
+
+    def test_traced_func_linear(self):
+        result = self.tracer.runfunc(traced_func_linear, 2, 5)
+        self.assertEqual(result, 7)
+
+        # all lines are executed once
+        expected = {}
+        firstlineno = get_firstlineno(traced_func_linear)
+        for i in range(1, 5):
+            expected[(self.my_py_filename, firstlineno +  i)] = 1
+
+        self.assertEqual(self.tracer.results().counts, expected)
+
+    def test_traced_func_loop(self):
+        self.tracer.runfunc(traced_func_loop, 2, 3)
+
+        firstlineno = get_firstlineno(traced_func_loop)
+        expected = {
+            (self.my_py_filename, firstlineno + 1): 1,
+            (self.my_py_filename, firstlineno + 2): 6,
+            (self.my_py_filename, firstlineno + 3): 5,
+            (self.my_py_filename, firstlineno + 4): 1,
+        }
+        self.assertEqual(self.tracer.results().counts, expected)
+
+    def test_traced_func_importing(self):
+        self.tracer.runfunc(traced_func_importing, 2, 5)
+
+        firstlineno = get_firstlineno(traced_func_importing)
+        expected = {
+            (self.my_py_filename, firstlineno + 1): 1,
+            (fix_ext_py(testmod.__file__), 2): 1,
+            (fix_ext_py(testmod.__file__), 3): 1,
+        }
+
+        self.assertEqual(self.tracer.results().counts, expected)
+
+    def test_trace_func_generator(self):
+        self.tracer.runfunc(traced_func_calling_generator)
+
+        firstlineno_calling = get_firstlineno(traced_func_calling_generator)
+        firstlineno_gen = get_firstlineno(traced_func_generator)
+        expected = {
+            (self.my_py_filename, firstlineno_calling + 1): 1,
+            (self.my_py_filename, firstlineno_calling + 2): 11,
+            (self.my_py_filename, firstlineno_calling + 3): 10,
+            (self.my_py_filename, firstlineno_gen + 1): 1,
+            (self.my_py_filename, firstlineno_gen + 2): 11,
+            (self.my_py_filename, firstlineno_gen + 3): 10,
+        }
+        self.assertEqual(self.tracer.results().counts, expected)
+
+    def test_trace_list_comprehension(self):
+        self.tracer.runfunc(traced_caller_list_comprehension)
+
+        firstlineno_calling = get_firstlineno(traced_caller_list_comprehension)
+        firstlineno_called = get_firstlineno(traced_doubler)
+        expected = {
+            (self.my_py_filename, firstlineno_calling + 1): 1,
+            # List compehentions work differently in 3.x, so the count
+            # below changed compared to 2.x.
+            (self.my_py_filename, firstlineno_calling + 2): 12,
+            (self.my_py_filename, firstlineno_calling + 3): 1,
+            (self.my_py_filename, firstlineno_called + 1): 10,
+        }
+        self.assertEqual(self.tracer.results().counts, expected)
+
+
+    def test_linear_methods(self):
+        # XXX todo: later add 'static_method_linear' and 'class_method_linear'
+        # here, once issue1764286 is resolved
+        #
+        for methname in ['inst_method_linear',]:
+            tracer = Trace(count=1, trace=0, countfuncs=0, countcallers=0)
+            traced_obj = TracedClass(25)
+            method = getattr(traced_obj, methname)
+            tracer.runfunc(method, 20)
+
+            firstlineno = get_firstlineno(method)
+            expected = {
+                (self.my_py_filename, firstlineno + 1): 1,
+            }
+            self.assertEqual(tracer.results().counts, expected)
+
+
+class TestRunExecCounts(unittest.TestCase):
+    """A simple sanity test of line-counting, via runctx (exec)"""
+    def setUp(self):
+        self.my_py_filename = fix_ext_py(__file__)
+
+    def test_exec_counts(self):
+        self.tracer = Trace(count=1, trace=0, countfuncs=0, countcallers=0)
+        code = r'''traced_func_loop(2, 5)'''
+        code = compile(code, __file__, 'exec')
+        self.tracer.runctx(code, globals(), vars())
+
+        firstlineno = get_firstlineno(traced_func_loop)
+        expected = {
+            (self.my_py_filename, firstlineno + 1): 1,
+            (self.my_py_filename, firstlineno + 2): 6,
+            (self.my_py_filename, firstlineno + 3): 5,
+            (self.my_py_filename, firstlineno + 4): 1,
+        }
+
+        # When used through 'run', some other spurios counts are produced, like
+        # the settrace of threading, which we ignore, just making sure that the
+        # counts fo traced_func_loop were right.
+        #
+        for k in expected.keys():
+            self.assertEqual(self.tracer.results().counts[k], expected[k])
+
+
+class TestFuncs(unittest.TestCase):
+    """White-box testing of funcs tracing"""
+    def setUp(self):
+        self.tracer = Trace(count=0, trace=0, countfuncs=1)
+        self.filemod = my_file_and_modname()
+
+    def test_simple_caller(self):
+        self.tracer.runfunc(traced_func_simple_caller, 1)
+
+        expected = {
+            self.filemod + ('traced_func_simple_caller',): 1,
+            self.filemod + ('traced_func_linear',): 1,
+        }
+        self.assertEqual(self.tracer.results().calledfuncs, expected)
+
+    def test_loop_caller_importing(self):
+        self.tracer.runfunc(traced_func_importing_caller, 1)
+
+        expected = {
+            self.filemod + ('traced_func_simple_caller',): 1,
+            self.filemod + ('traced_func_linear',): 1,
+            self.filemod + ('traced_func_importing_caller',): 1,
+            self.filemod + ('traced_func_importing',): 1,
+            (fix_ext_py(testmod.__file__), 'testmod', 'func'): 1,
+        }
+        self.assertEqual(self.tracer.results().calledfuncs, expected)
+
+    def test_inst_method_calling(self):
+        obj = TracedClass(20)
+        self.tracer.runfunc(obj.inst_method_calling, 1)
+
+        expected = {
+            self.filemod + ('TracedClass.inst_method_calling',): 1,
+            self.filemod + ('TracedClass.inst_method_linear',): 1,
+            self.filemod + ('traced_func_linear',): 1,
+        }
+        self.assertEqual(self.tracer.results().calledfuncs, expected)
+
+
+class TestCallers(unittest.TestCase):
+    """White-box testing of callers tracing"""
+    def setUp(self):
+        self.tracer = Trace(count=0, trace=0, countcallers=1)
+        self.filemod = my_file_and_modname()
+
+    def test_loop_caller_importing(self):
+        self.tracer.runfunc(traced_func_importing_caller, 1)
+
+        expected = {
+            ((os.path.splitext(trace.__file__)[0] + '.py', 'trace', 'Trace.runfunc'),
+                (self.filemod + ('traced_func_importing_caller',))): 1,
+            ((self.filemod + ('traced_func_simple_caller',)),
+                (self.filemod + ('traced_func_linear',))): 1,
+            ((self.filemod + ('traced_func_importing_caller',)),
+                (self.filemod + ('traced_func_simple_caller',))): 1,
+            ((self.filemod + ('traced_func_importing_caller',)),
+                (self.filemod + ('traced_func_importing',))): 1,
+            ((self.filemod + ('traced_func_importing',)),
+                (fix_ext_py(testmod.__file__), 'testmod', 'func')): 1,
+        }
+        self.assertEqual(self.tracer.results().callers, expected)
+
+
+# Created separately for issue #3821
 class TestCoverage(unittest.TestCase):
     def tearDown(self):
         rmtree(TESTFN)
@@ -34,7 +310,6 @@
                              trace=0, count=1)
         with captured_stdout() as stdout:
             self._coverage(tracer)
-        self.assertEquals(stdout.getvalue(), "")
         if os.path.exists(TESTFN):
             files = os.listdir(TESTFN)
             self.assertEquals(files, [])
@@ -43,5 +318,6 @@
 def test_main():
     run_unittest(__name__)
 
-if __name__ == "__main__":
+
+if __name__ == '__main__':
     test_main()