diff --git a/src/dc_strencode.rs b/src/dc_strencode.rs
index bc5ad7164..a0a73cf50 100644
--- a/src/dc_strencode.rs
+++ b/src/dc_strencode.rs
@@ -728,6 +728,7 @@ pub unsafe fn dc_decode_ext_header(to_decode: *const libc::c_char) -> *mut libc:
 #[cfg(test)]
 mod tests {
     use super::*;
+    use std::ffi::CStr;
 
     #[test]
     fn test_isalnum() {
@@ -735,4 +736,159 @@ mod tests {
         assert_eq!(isalnum('5' as libc::c_int), 1);
         assert_eq!(isalnum('Q' as libc::c_int), 1);
     }
+
+    #[test]
+    fn test_dc_decode_header_words() {
+        unsafe {
+            let mut buf1: *mut libc::c_char = dc_decode_header_words(
+                b"=?utf-8?B?dGVzdMOkw7bDvC50eHQ=?=\x00" as *const u8 as *const libc::c_char,
+            );
+            assert_eq!(
+                strcmp(
+                    buf1,
+                    b"test\xc3\xa4\xc3\xb6\xc3\xbc.txt\x00" as *const u8 as *const libc::c_char
+                ),
+                0
+            );
+            free(buf1 as *mut libc::c_void);
+
+            buf1 =
+                dc_decode_header_words(b"just ascii test\x00" as *const u8 as *const libc::c_char);
+            assert_eq!(CStr::from_ptr(buf1).to_str().unwrap(), "just ascii test");
+            free(buf1 as *mut libc::c_void);
+
+            buf1 = dc_encode_header_words(b"abcdef\x00" as *const u8 as *const libc::c_char);
+            assert_eq!(CStr::from_ptr(buf1).to_str().unwrap(), "abcdef");
+            free(buf1 as *mut libc::c_void);
+
+            buf1 = dc_encode_header_words(
+                b"test\xc3\xa4\xc3\xb6\xc3\xbc.txt\x00" as *const u8 as *const libc::c_char,
+            );
+            assert_eq!(
+                strncmp(buf1, b"=?utf-8\x00" as *const u8 as *const libc::c_char, 7),
+                0
+            );
+
+            let buf2: *mut libc::c_char = dc_decode_header_words(buf1);
+            assert_eq!(
+                strcmp(
+                    buf2,
+                    b"test\xc3\xa4\xc3\xb6\xc3\xbc.txt\x00" as *const u8 as *const libc::c_char
+                ),
+                0
+            );
+            free(buf1 as *mut libc::c_void);
+            free(buf2 as *mut libc::c_void);
+
+            buf1 = dc_decode_header_words(
+                b"=?ISO-8859-1?Q?attachment=3B=0D=0A_filename=3D?= =?ISO-8859-1?Q?=22test=E4=F6=FC=2Etxt=22=3B=0D=0A_size=3D39?=\x00" as *const u8 as *const libc::c_char
+            );
+            assert_eq!(
+                strcmp(
+                    buf1,
+                    b"attachment;\r\n filename=\"test\xc3\xa4\xc3\xb6\xc3\xbc.txt\";\r\n size=39\x00" as *const u8 as *const libc::c_char,
+
+                ),
+                0
+            );
+            free(buf1 as *mut libc::c_void);
+        }
+    }
+
+    #[test]
+    fn test_dc_encode_ext_header() {
+        unsafe {
+            let mut buf1 = dc_encode_ext_header(
+                b"Bj\xc3\xb6rn Petersen\x00" as *const u8 as *const libc::c_char,
+            );
+            assert_eq!(
+                CStr::from_ptr(buf1).to_str().unwrap(),
+                "utf-8\'\'Bj%C3%B6rn%20Petersen"
+            );
+            let buf2 = dc_decode_ext_header(buf1);
+            assert_eq!(
+                strcmp(
+                    buf2,
+                    b"Bj\xc3\xb6rn Petersen\x00" as *const u8 as *const libc::c_char,
+                ),
+                0
+            );
+            free(buf1 as *mut libc::c_void);
+            free(buf2 as *mut libc::c_void);
+
+            buf1 = dc_decode_ext_header(
+                b"iso-8859-1\'en\'%A3%20rates\x00" as *const u8 as *const libc::c_char,
+            );
+            assert_eq!(
+                strcmp(
+                    buf1,
+                    b"\xc2\xa3 rates\x00" as *const u8 as *const libc::c_char,
+                ),
+                0
+            );
+            free(buf1 as *mut libc::c_void);
+
+            buf1 = dc_decode_ext_header(b"wrong\'format\x00" as *const u8 as *const libc::c_char);
+            assert_eq!(
+                strcmp(
+                    buf1,
+                    b"wrong\'format\x00" as *const u8 as *const libc::c_char,
+                ),
+                0
+            );
+            free(buf1 as *mut libc::c_void);
+
+            buf1 = dc_decode_ext_header(b"\'\'\x00" as *const u8 as *const libc::c_char);
+            assert_eq!(
+                strcmp(buf1, b"\'\'\x00" as *const u8 as *const libc::c_char),
+                0
+            );
+            free(buf1 as *mut libc::c_void);
+
+            buf1 = dc_decode_ext_header(b"x\'\'\x00" as *const u8 as *const libc::c_char);
+            assert_eq!(strcmp(buf1, b"\x00" as *const u8 as *const libc::c_char), 0);
+            free(buf1 as *mut libc::c_void);
+
+            buf1 = dc_decode_ext_header(b"\'\x00" as *const u8 as *const libc::c_char);
+            assert_eq!(
+                strcmp(buf1, b"\'\x00" as *const u8 as *const libc::c_char),
+                0
+            );
+            free(buf1 as *mut libc::c_void);
+
+            buf1 = dc_decode_ext_header(b"\x00" as *const u8 as *const libc::c_char);
+            assert_eq!(strcmp(buf1, b"\x00" as *const u8 as *const libc::c_char), 0);
+            free(buf1 as *mut libc::c_void);
+        }
+    }
+
+    #[test]
+    fn test_dc_needs_ext_header() {
+        unsafe {
+            assert_eq!(
+                dc_needs_ext_header(b"Bj\xc3\xb6rn\x00" as *const u8 as *const libc::c_char),
+                true
+            );
+            assert_eq!(
+                dc_needs_ext_header(b"Bjoern\x00" as *const u8 as *const libc::c_char),
+                false
+            );
+            assert_eq!(
+                dc_needs_ext_header(b"\x00" as *const u8 as *const libc::c_char),
+                false
+            );
+            assert_eq!(
+                dc_needs_ext_header(b" \x00" as *const u8 as *const libc::c_char),
+                true
+            );
+            assert_eq!(
+                dc_needs_ext_header(b"a b\x00" as *const u8 as *const libc::c_char),
+                true
+            );
+            assert_eq!(
+                dc_needs_ext_header(0 as *const u8 as *const libc::c_char),
+                false
+            );
+        }
+    }
 }
diff --git a/tests/stress.rs b/tests/stress.rs
index 50bb3e462..ffaa84437 100644
--- a/tests/stress.rs
+++ b/tests/stress.rs
@@ -510,313 +510,6 @@ unsafe fn stress_functions(context: &dc_context_t) {
     } else {
     };
     free(buf1 as *mut libc::c_void);
-    buf1 = dc_decode_header_words(
-        b"=?utf-8?B?dGVzdMOkw7bDvC50eHQ=?=\x00" as *const u8 as *const libc::c_char,
-    );
-    if 0 != !(strcmp(
-        buf1,
-        b"test\xc3\xa4\xc3\xb6\xc3\xbc.txt\x00" as *const u8 as *const libc::c_char,
-    ) == 0i32) as libc::c_int as libc::c_long
-    {
-        __assert_rtn(
-            (*::std::mem::transmute::<&[u8; 17], &[libc::c_char; 17]>(b"stress_functions\x00"))
-                .as_ptr(),
-            b"../cmdline/stress.c\x00" as *const u8 as *const libc::c_char,
-            538i32,
-            b"strcmp(buf1, \"test\xc3\xa4\xc3\xb6\xc3\xbc.txt\")==0\x00" as *const u8
-                as *const libc::c_char,
-        );
-    } else {
-    };
-    free(buf1 as *mut libc::c_void);
-    buf1 = dc_decode_header_words(b"just ascii test\x00" as *const u8 as *const libc::c_char);
-    if 0 != !(strcmp(
-        buf1,
-        b"just ascii test\x00" as *const u8 as *const libc::c_char,
-    ) == 0i32) as libc::c_int as libc::c_long
-    {
-        __assert_rtn(
-            (*::std::mem::transmute::<&[u8; 17], &[libc::c_char; 17]>(b"stress_functions\x00"))
-                .as_ptr(),
-            b"../cmdline/stress.c\x00" as *const u8 as *const libc::c_char,
-            542i32,
-            b"strcmp(buf1, \"just ascii test\")==0\x00" as *const u8 as *const libc::c_char,
-        );
-    } else {
-    };
-    free(buf1 as *mut libc::c_void);
-    buf1 = dc_encode_header_words(b"abcdef\x00" as *const u8 as *const libc::c_char);
-    if 0 != !(strcmp(buf1, b"abcdef\x00" as *const u8 as *const libc::c_char) == 0i32)
-        as libc::c_int as libc::c_long
-    {
-        __assert_rtn(
-            (*::std::mem::transmute::<&[u8; 17], &[libc::c_char; 17]>(b"stress_functions\x00"))
-                .as_ptr(),
-            b"../cmdline/stress.c\x00" as *const u8 as *const libc::c_char,
-            546i32,
-            b"strcmp(buf1, \"abcdef\")==0\x00" as *const u8 as *const libc::c_char,
-        );
-    } else {
-    };
-    free(buf1 as *mut libc::c_void);
-    buf1 = dc_encode_header_words(
-        b"test\xc3\xa4\xc3\xb6\xc3\xbc.txt\x00" as *const u8 as *const libc::c_char,
-    );
-    if 0 != !(strncmp(buf1, b"=?utf-8\x00" as *const u8 as *const libc::c_char, 7) == 0i32)
-        as libc::c_int as libc::c_long
-    {
-        __assert_rtn(
-            (*::std::mem::transmute::<&[u8; 17], &[libc::c_char; 17]>(b"stress_functions\x00"))
-                .as_ptr(),
-            b"../cmdline/stress.c\x00" as *const u8 as *const libc::c_char,
-            550i32,
-            b"strncmp(buf1, \"=?utf-8\", 7)==0\x00" as *const u8 as *const libc::c_char,
-        );
-    } else {
-    };
-    buf2 = dc_decode_header_words(buf1);
-    if 0 != !(strcmp(
-        b"test\xc3\xa4\xc3\xb6\xc3\xbc.txt\x00" as *const u8 as *const libc::c_char,
-        buf2,
-    ) == 0i32) as libc::c_int as libc::c_long
-    {
-        __assert_rtn(
-            (*::std::mem::transmute::<&[u8; 17], &[libc::c_char; 17]>(b"stress_functions\x00"))
-                .as_ptr(),
-            b"../cmdline/stress.c\x00" as *const u8 as *const libc::c_char,
-            552i32,
-            b"strcmp(\"test\xc3\xa4\xc3\xb6\xc3\xbc.txt\", buf2)==0\x00" as *const u8
-                as *const libc::c_char,
-        );
-    } else {
-    };
-    free(buf1 as *mut libc::c_void);
-    free(buf2 as *mut libc::c_void);
-    buf1 =
-        dc_decode_header_words(b"=?ISO-8859-1?Q?attachment=3B=0D=0A_filename=3D?= =?ISO-8859-1?Q?=22test=E4=F6=FC=2Etxt=22=3B=0D=0A_size=3D39?=\x00"
-                                   as *const u8 as *const libc::c_char);
-    if 0 != !(strcmp(
-        buf1,
-        b"attachment;\r\n filename=\"test\xc3\xa4\xc3\xb6\xc3\xbc.txt\";\r\n size=39\x00"
-            as *const u8 as *const libc::c_char,
-    ) == 0i32) as libc::c_int as libc::c_long
-    {
-        __assert_rtn((*::std::mem::transmute::<&[u8; 17],
-                                               &[libc::c_char; 17]>(b"stress_functions\x00")).as_ptr(),
-                     b"../cmdline/stress.c\x00" as *const u8 as
-                         *const libc::c_char, 557i32,
-                     b"strcmp(buf1, \"attachment;\\r\\n filename=\\\"test\xc3\xa4\xc3\xb6\xc3\xbc.txt\\\";\\r\\n size=39\")==0\x00"
-                         as *const u8 as *const libc::c_char);
-    } else {
-    };
-    free(buf1 as *mut libc::c_void);
-    buf1 = dc_encode_ext_header(b"Bj\xc3\xb6rn Petersen\x00" as *const u8 as *const libc::c_char);
-    if 0 != !(strcmp(
-        buf1,
-        b"utf-8\'\'Bj%C3%B6rn%20Petersen\x00" as *const u8 as *const libc::c_char,
-    ) == 0i32) as libc::c_int as libc::c_long
-    {
-        __assert_rtn(
-            (*::std::mem::transmute::<&[u8; 17], &[libc::c_char; 17]>(b"stress_functions\x00"))
-                .as_ptr(),
-            b"../cmdline/stress.c\x00" as *const u8 as *const libc::c_char,
-            561i32,
-            b"strcmp(buf1, \"utf-8\'\'Bj%C3%B6rn%20Petersen\") == 0\x00" as *const u8
-                as *const libc::c_char,
-        );
-    } else {
-    };
-    buf2 = dc_decode_ext_header(buf1);
-    if 0 != !(strcmp(
-        buf2,
-        b"Bj\xc3\xb6rn Petersen\x00" as *const u8 as *const libc::c_char,
-    ) == 0i32) as libc::c_int as libc::c_long
-    {
-        __assert_rtn(
-            (*::std::mem::transmute::<&[u8; 17], &[libc::c_char; 17]>(b"stress_functions\x00"))
-                .as_ptr(),
-            b"../cmdline/stress.c\x00" as *const u8 as *const libc::c_char,
-            563i32,
-            b"strcmp(buf2, \"Bj\xc3\xb6rn Petersen\") == 0\x00" as *const u8 as *const libc::c_char,
-        );
-    } else {
-    };
-    free(buf1 as *mut libc::c_void);
-    free(buf2 as *mut libc::c_void);
-    buf1 = dc_decode_ext_header(
-        b"iso-8859-1\'en\'%A3%20rates\x00" as *const u8 as *const libc::c_char,
-    );
-    if 0 != !(strcmp(
-        buf1,
-        b"\xc2\xa3 rates\x00" as *const u8 as *const libc::c_char,
-    ) == 0i32) as libc::c_int as libc::c_long
-    {
-        __assert_rtn(
-            (*::std::mem::transmute::<&[u8; 17], &[libc::c_char; 17]>(b"stress_functions\x00"))
-                .as_ptr(),
-            b"../cmdline/stress.c\x00" as *const u8 as *const libc::c_char,
-            568i32,
-            b"strcmp(buf1, \"\xc2\xa3 rates\") == 0\x00" as *const u8 as *const libc::c_char,
-        );
-    } else {
-    };
-    if 0 != !(strcmp(
-        buf1,
-        b"\xc2\xa3 rates\x00" as *const u8 as *const libc::c_char,
-    ) == 0i32) as libc::c_int as libc::c_long
-    {
-        __assert_rtn(
-            (*::std::mem::transmute::<&[u8; 17], &[libc::c_char; 17]>(b"stress_functions\x00"))
-                .as_ptr(),
-            b"../cmdline/stress.c\x00" as *const u8 as *const libc::c_char,
-            569i32,
-            b"strcmp(buf1, \"\\xC2\\xA3 rates\") == 0\x00" as *const u8 as *const libc::c_char,
-        );
-    } else {
-    };
-    free(buf1 as *mut libc::c_void);
-    buf1 = dc_decode_ext_header(b"wrong\'format\x00" as *const u8 as *const libc::c_char);
-    if 0 != !(strcmp(
-        buf1,
-        b"wrong\'format\x00" as *const u8 as *const libc::c_char,
-    ) == 0i32) as libc::c_int as libc::c_long
-    {
-        __assert_rtn(
-            (*::std::mem::transmute::<&[u8; 17], &[libc::c_char; 17]>(b"stress_functions\x00"))
-                .as_ptr(),
-            b"../cmdline/stress.c\x00" as *const u8 as *const libc::c_char,
-            573i32,
-            b"strcmp(buf1, \"wrong\'format\") == 0\x00" as *const u8 as *const libc::c_char,
-        );
-    } else {
-    };
-    free(buf1 as *mut libc::c_void);
-    buf1 = dc_decode_ext_header(b"\'\'\x00" as *const u8 as *const libc::c_char);
-    if 0 != !(strcmp(buf1, b"\'\'\x00" as *const u8 as *const libc::c_char) == 0i32) as libc::c_int
-        as libc::c_long
-    {
-        __assert_rtn(
-            (*::std::mem::transmute::<&[u8; 17], &[libc::c_char; 17]>(b"stress_functions\x00"))
-                .as_ptr(),
-            b"../cmdline/stress.c\x00" as *const u8 as *const libc::c_char,
-            577i32,
-            b"strcmp(buf1, \"\'\'\") == 0\x00" as *const u8 as *const libc::c_char,
-        );
-    } else {
-    };
-    free(buf1 as *mut libc::c_void);
-    buf1 = dc_decode_ext_header(b"x\'\'\x00" as *const u8 as *const libc::c_char);
-    if 0 != !(strcmp(buf1, b"\x00" as *const u8 as *const libc::c_char) == 0i32) as libc::c_int
-        as libc::c_long
-    {
-        __assert_rtn(
-            (*::std::mem::transmute::<&[u8; 17], &[libc::c_char; 17]>(b"stress_functions\x00"))
-                .as_ptr(),
-            b"../cmdline/stress.c\x00" as *const u8 as *const libc::c_char,
-            581i32,
-            b"strcmp(buf1, \"\") == 0\x00" as *const u8 as *const libc::c_char,
-        );
-    } else {
-    };
-    free(buf1 as *mut libc::c_void);
-    buf1 = dc_decode_ext_header(b"\'\x00" as *const u8 as *const libc::c_char);
-    if 0 != !(strcmp(buf1, b"\'\x00" as *const u8 as *const libc::c_char) == 0i32) as libc::c_int
-        as libc::c_long
-    {
-        __assert_rtn(
-            (*::std::mem::transmute::<&[u8; 17], &[libc::c_char; 17]>(b"stress_functions\x00"))
-                .as_ptr(),
-            b"../cmdline/stress.c\x00" as *const u8 as *const libc::c_char,
-            585i32,
-            b"strcmp(buf1, \"\'\") == 0\x00" as *const u8 as *const libc::c_char,
-        );
-    } else {
-    };
-    free(buf1 as *mut libc::c_void);
-    buf1 = dc_decode_ext_header(b"\x00" as *const u8 as *const libc::c_char);
-    if 0 != !(strcmp(buf1, b"\x00" as *const u8 as *const libc::c_char) == 0i32) as libc::c_int
-        as libc::c_long
-    {
-        __assert_rtn(
-            (*::std::mem::transmute::<&[u8; 17], &[libc::c_char; 17]>(b"stress_functions\x00"))
-                .as_ptr(),
-            b"../cmdline/stress.c\x00" as *const u8 as *const libc::c_char,
-            589i32,
-            b"strcmp(buf1, \"\") == 0\x00" as *const u8 as *const libc::c_char,
-        );
-    } else {
-    };
-    free(buf1 as *mut libc::c_void);
-    if 0 != (!dc_needs_ext_header(b"Bj\xc3\xb6rn\x00" as *const u8 as *const libc::c_char))
-        as libc::c_int as libc::c_long
-    {
-        __assert_rtn(
-            (*::std::mem::transmute::<&[u8; 17], &[libc::c_char; 17]>(b"stress_functions\x00"))
-                .as_ptr(),
-            b"../cmdline/stress.c\x00" as *const u8 as *const libc::c_char,
-            592i32,
-            b"dc_needs_ext_header(\"Bj\xc3\xb6rn\")\x00" as *const u8 as *const libc::c_char,
-        );
-    } else {
-    };
-    if 0 != (dc_needs_ext_header(b"Bjoern\x00" as *const u8 as *const libc::c_char)) as libc::c_int
-        as libc::c_long
-    {
-        __assert_rtn(
-            (*::std::mem::transmute::<&[u8; 17], &[libc::c_char; 17]>(b"stress_functions\x00"))
-                .as_ptr(),
-            b"../cmdline/stress.c\x00" as *const u8 as *const libc::c_char,
-            593i32,
-            b"!dc_needs_ext_header(\"Bjoern\")\x00" as *const u8 as *const libc::c_char,
-        );
-    } else {
-    };
-    if 0 != (dc_needs_ext_header(b"\x00" as *const u8 as *const libc::c_char)) as libc::c_int
-        as libc::c_long
-    {
-        __assert_rtn(
-            (*::std::mem::transmute::<&[u8; 17], &[libc::c_char; 17]>(b"stress_functions\x00"))
-                .as_ptr(),
-            b"../cmdline/stress.c\x00" as *const u8 as *const libc::c_char,
-            594i32,
-            b"!dc_needs_ext_header(\"\")\x00" as *const u8 as *const libc::c_char,
-        );
-    } else {
-    };
-    if 0 != (!dc_needs_ext_header(b" \x00" as *const u8 as *const libc::c_char)) as libc::c_int
-        as libc::c_long
-    {
-        __assert_rtn(
-            (*::std::mem::transmute::<&[u8; 17], &[libc::c_char; 17]>(b"stress_functions\x00"))
-                .as_ptr(),
-            b"../cmdline/stress.c\x00" as *const u8 as *const libc::c_char,
-            595i32,
-            b"dc_needs_ext_header(\" \")\x00" as *const u8 as *const libc::c_char,
-        );
-    } else {
-    };
-    if 0 != (!dc_needs_ext_header(b"a b\x00" as *const u8 as *const libc::c_char)) as libc::c_int
-        as libc::c_long
-    {
-        __assert_rtn(
-            (*::std::mem::transmute::<&[u8; 17], &[libc::c_char; 17]>(b"stress_functions\x00"))
-                .as_ptr(),
-            b"../cmdline/stress.c\x00" as *const u8 as *const libc::c_char,
-            596i32,
-            b"dc_needs_ext_header(\"a b\")\x00" as *const u8 as *const libc::c_char,
-        );
-    } else {
-    };
-    if 0 != (dc_needs_ext_header(0 as *const libc::c_char)) as libc::c_int as libc::c_long {
-        __assert_rtn(
-            (*::std::mem::transmute::<&[u8; 17], &[libc::c_char; 17]>(b"stress_functions\x00"))
-                .as_ptr(),
-            b"../cmdline/stress.c\x00" as *const u8 as *const libc::c_char,
-            597i32,
-            b"!dc_needs_ext_header(NULL)\x00" as *const u8 as *const libc::c_char,
-        );
-    } else {
-    };
     buf1 = dc_encode_modified_utf7(
         b"Bj\xc3\xb6rn Petersen\x00" as *const u8 as *const libc::c_char,
         1i32,