diff --git a/check50/_api.py b/check50/_api.py
index bb7f2e0..be757c7 100644
--- a/check50/_api.py
+++ b/check50/_api.py
@@ -161,10 +161,16 @@ def __init__(self, command, env={}):
         full_env = os.environ.copy()
         full_env.update(env)
 
+        # load in env into bash manually via export commands
+        bash_command = ""
+        for key in full_env:
+            bash_command += "export {}={} && ".format(shlex.quote(key), shlex.quote(full_env[key]))
+        bash_command += command
+
         # Workaround for OSX pexpect bug http://pexpect.readthedocs.io/en/stable/commonissues.html#truncated-output-just-before-child-exits
         # Workaround from https://github.com/pexpect/pexpect/issues/373
-        command = "bash -c {}".format(shlex.quote(command))
-        self.process = pexpect.spawn(command, encoding="utf-8", echo=False, env=full_env)
+        command = "bash -c {}".format(shlex.quote(bash_command))
+        self.process = pexpect.spawn(command, encoding="utf-8", echo=False)
 
     def stdin(self, line, str_line=None, prompt=True, timeout=3):
         """
diff --git a/check50/_simple.py b/check50/_simple.py
index 9339b05..ca4a188 100644
--- a/check50/_simple.py
+++ b/check50/_simple.py
@@ -59,7 +59,7 @@ def _compile_check(name, check):
     if check_name[0].isdigit():
         check_name = f"_{check_name}"
 
-    if not re.match("\w+", check_name):
+    if not re.match(r"\w+", check_name):
         raise CompileError(
                 _("{} is not a valid name for a check; check names should consist only of alphanumeric characters, underscores, and spaces").format(name))
 
diff --git a/check50/c.py b/check50/c.py
index d38078f..021d177 100644
--- a/check50/c.py
+++ b/check50/c.py
@@ -55,7 +55,8 @@ def compile(*files, exe_name=None, cc=CC, max_log_lines=50, **cflags):
 
     out_flag = f" -o {exe_name} " if exe_name is not None else " "
 
-    process = run(f"{cc} {files}{out_flag}{flags}")
+    proc_str = f"{cc} {files}{out_flag}{flags}"
+    process = run(proc_str)
 
     # Strip out ANSI codes
     stdout = re.sub(r"\x1B\[[0-?]*[ -/]*[@-~]", "",  process.stdout())
diff --git a/check50/regex.py b/check50/regex.py
index 215c65a..2b20786 100644
--- a/check50/regex.py
+++ b/check50/regex.py
@@ -7,16 +7,16 @@ def decimal(number):
 
     In case of a positive number::
 
-        (?<![\d\-])number(?!(\.?\d))
+        (?<![\\d\\-])number(?!(\\.?\\d))
 
     In case of a negative number::
 
-        number(?!(\.?\d))
+        number(?!(\\.?\\d))
 
-    :code:`(?<![\d\-])` = negative lookbehind, \
+    :code:`(?<![\\d\\-])` = negative lookbehind, \
         asserts that there are no digits and no - in front of the number.
 
-    :code:`(?!(\.?\d))` = negative lookahead, \
+    :code:`(?!(\\.?\\d))` = negative lookahead, \
         asserts that there are no digits and no additional . followed by digits after the number.
 
     :param number: the number to match in the regex
diff --git a/setup.py b/setup.py
index 550225f..b82a0c9 100644
--- a/setup.py
+++ b/setup.py
@@ -30,6 +30,6 @@
         "console_scripts": ["check50=check50.__main__:main"]
     },
     url="https://github.com/cs50/check50",
-    version="3.3.11",
+    version="3.3.12",
     include_package_data=True
 )
diff --git a/tests/c_tests.py b/tests/c_tests.py
index 6a3e02c..a98ee45 100644
--- a/tests/c_tests.py
+++ b/tests/c_tests.py
@@ -15,49 +15,63 @@
 CHECKS_DIRECTORY = pathlib.Path(__file__).absolute().parent / "checks"
 
 class Base(unittest.TestCase):
+    starting_dir = os.getcwd()
+
     def setUp(self):
         if not CLANG_INSTALLED:
             raise unittest.SkipTest("clang not installed")
-        if not VALGRIND_INSTALLED:
-            raise unittest.SkipTest("valgrind not installed")
+
+        # ensures each test starts from same cwd;
+        # 'chdir' would otherwise persist between tests
+        os.chdir(self.starting_dir)
+
+        # write c test files to temp directory
+        test_files = {}
+        os.chdir("test_files")
+        for file in os.listdir():
+            with open(file) as f:
+                test_files[file] = f.read()
 
         self.working_directory = tempfile.TemporaryDirectory()
         os.chdir(self.working_directory.name)
 
+        for file in test_files:
+            with open(file, "w") as f:
+                f.write(test_files[file])
+
     def tearDown(self):
         self.working_directory.cleanup()
 
 class TestCompile(Base):
     def test_compile_incorrect(self):
-        open("blank.c", "w").close()
-
         with self.assertRaises(check50.Failure):
             check50.c.compile("blank.c")
 
     def test_compile_hello_world(self):
-        with open("hello.c", "w") as f:
-            src =   '#include <stdio.h>\n'\
-                    'int main() {\n'\
-                    '    printf("hello, world!\\n");\n'\
-                    '}'
-            f.write(src)
-
         check50.c.compile("hello.c")
-
         self.assertTrue(os.path.isfile("hello"))
+
+class TestRun(Base):
+    def test_stdout_hello_world(self):
+        check50.c.compile("hello.c")
         check50.run("./hello").stdout("hello, world!", regex=False)
 
+    def test_stdin_cash(self):
+        check50.c.compile("cash.c", lcs50=True)
+        check50.run("./cash").stdin("42", prompt=True).stdout("5").exit()
+
 class TestValgrind(Base):
     def setUp(self):
         super().setUp()
+
+        # valgrind installation check moved to here from Base()
+        if not VALGRIND_INSTALLED:
+            raise unittest.SkipTest("valgrind not installed")
         if not (sys.platform == "linux" or sys.platform == "linux2"):
             raise unittest.SkipTest("skipping valgrind checks under anything other than Linux due to false positives")
 
     def test_no_leak(self):
         check50.internal.check_running = True
-        with open("foo.c", "w") as f:
-            src = 'int main() {}'
-            f.write(src)
 
         check50.c.compile("foo.c")
         with check50.internal.register:
@@ -66,13 +80,6 @@ def test_no_leak(self):
 
     def test_leak(self):
         check50.internal.check_running = True
-        with open("leak.c", "w") as f:
-            src =   '#include <stdlib.h>\n'\
-                    'void leak() {malloc(sizeof(int));}\n'\
-                    'int main() {\n'\
-                    '    leak();\n'\
-                    '}'
-            f.write(src)
 
         check50.c.compile("leak.c")
         with self.assertRaises(check50.Failure):
diff --git a/tests/test_files/blank.c b/tests/test_files/blank.c
new file mode 100644
index 0000000..e69de29
diff --git a/tests/test_files/cash.c b/tests/test_files/cash.c
new file mode 100644
index 0000000..f8ed03f
--- /dev/null
+++ b/tests/test_files/cash.c
@@ -0,0 +1,21 @@
+#include <cs50.h>
+#include <stdio.h>
+
+int main(void) {
+    int cents;
+    do {
+        cents = get_int("Cents? ");
+    }
+    while (cents < 0);
+
+    const int n_denominations = 4;
+    int denominations[n_denominations] = {1, 5, 10, 25};
+
+    int coins = 0;
+    for (int i = n_denominations - 1; i >= 0; i--) {
+        coins += cents / denominations[i];
+        cents %= denominations[i];
+    }
+
+    printf("%i\n", coins);
+}
diff --git a/tests/test_files/foo.c b/tests/test_files/foo.c
new file mode 100644
index 0000000..237c8ce
--- /dev/null
+++ b/tests/test_files/foo.c
@@ -0,0 +1 @@
+int main() {}
diff --git a/tests/test_files/hello.c b/tests/test_files/hello.c
new file mode 100644
index 0000000..a262b3f
--- /dev/null
+++ b/tests/test_files/hello.c
@@ -0,0 +1,5 @@
+#include <stdio.h>
+
+int main() {
+    printf("hello, world!\n");
+}
diff --git a/tests/test_files/leak.c b/tests/test_files/leak.c
new file mode 100644
index 0000000..e0e29f3
--- /dev/null
+++ b/tests/test_files/leak.c
@@ -0,0 +1,9 @@
+#include <stdlib.h>
+
+void leak() {
+    malloc(sizeof(int));
+}
+
+int main() {
+    leak();
+}