fixed, cleaned up, and added tests to PrintField
diff --git a/aos/common/print_field_helpers.h b/aos/common/print_field_helpers.h
index 50ac01e..0dd2fab 100644
--- a/aos/common/print_field_helpers.h
+++ b/aos/common/print_field_helpers.h
@@ -10,30 +10,30 @@
 template<typename T>
 inline bool PrintInteger(char *buf, T val, size_t *output) {
   static const bool is_signed = ::std::is_signed<T>::value;
+  const bool is_negative =
+      is_signed ? (val & (static_cast<T>(1) << (sizeof(T) * 8 - 1))) : false;
 
   size_t len = 0;
-  if (is_signed && val <= 0) {
-    while (*output >= len && (val != 0 || len == 0)) {
+  if (is_negative) {
+    do {
+      if (len == *output) return false;
       buf[len++] = '0' - (val % 10);
       val /= 10;
-    }
+    } while (val != 0);
+    if (len == *output) return false;
     buf[len++] = '-';
   } else {
-    while (*output >= len && (val != 0 || len == 0)) {
+    do {
+      if (len == *output) return false;
       buf[len++] = '0' + (val % 10);
       val /= 10;
-    }
+    } while (val != 0);
   }
-  // If we have enough space.
-  if (*output >= len) {
-    for (size_t i = 0; i < (len >> 1); i++) {
-      std::swap(buf[len - 1 - i], buf[i]);
-    }
-    *output -= len;
-    return true;
-  } else {
-    return false;
+  for (size_t i = 0; i < (len >> 1); i++) {
+    std::swap(buf[len - 1 - i], buf[i]);
   }
+  *output -= len;
+  return true;
 }
 
 }  // namespace aos
diff --git a/aos/common/queue_types_test.cc b/aos/common/queue_types_test.cc
index 26b5a87..96b7dfb 100644
--- a/aos/common/queue_types_test.cc
+++ b/aos/common/queue_types_test.cc
@@ -1,6 +1,8 @@
 #include "aos/common/queue_types.h"
 
 #include <memory>
+#include <limits>
+#include <string>
 
 #include "gtest/gtest.h"
 
@@ -52,9 +54,6 @@
   }
 };
 
-// TODO(brians): Do a better job testing PrintField with the types that have
-// specialized implementations.
-
 TEST_F(QueueTypesTest, Serialization) {
   char buffer[512];
   ssize_t size;
@@ -81,24 +80,76 @@
   EXPECT_TRUE(Equal(kTestType1, *deserialized));
 }
 
-class PrintFieldTest : public ::testing::Test {
+class PrintMessageTest : public ::testing::Test {
  public:
   char input[128], output[128];
   size_t input_bytes, output_bytes;
 };
-typedef PrintFieldTest PrintMessageTest;
+
+class PrintFieldTest : public PrintMessageTest {
+ public:
+  template <typename T>
+  void TestInteger(T value, ::std::string result) {
+    input_bytes = sizeof(value);
+    to_network(&value, input);
+    output_bytes = sizeof(output);
+    ASSERT_TRUE(
+        PrintField(output, &output_bytes, input, &input_bytes, TypeID<T>::id));
+    EXPECT_EQ(0u, input_bytes);
+    EXPECT_EQ(sizeof(output) - result.size(), output_bytes);
+    EXPECT_EQ(result, ::std::string(output, sizeof(output) - output_bytes));
+  }
+
+  template <typename T>
+  void TestAllIntegers(T multiple) {
+    for (T i = ::std::numeric_limits<T>::min();
+         i < ::std::numeric_limits<T>::max() - multiple; i += multiple) {
+      TestInteger<T>(i, ::std::to_string(i));
+    }
+  }
+};
 
 TEST_F(PrintFieldTest, Basic) {
-  static const uint16_t kData = 971;
-  input_bytes = sizeof(kData);
-  to_network(&kData, input);
+  TestInteger<uint16_t>(971, "971");
+  TestInteger<uint8_t>(8, "8");
+  TestInteger<uint8_t>(254, "254");
+  TestInteger<uint8_t>(0, "0");
+  TestInteger<int8_t>(254, "-2");
+  TestInteger<int8_t>(67, "67");
+  TestInteger<int8_t>(0, "0");
+
+  input_bytes = 1;
+  input[0] = 1;
   output_bytes = sizeof(output);
   ASSERT_TRUE(PrintField(output, &output_bytes, input, &input_bytes,
-                         Structure::GetType()->fields[1]->type));
+                         queue_primitive_types::bool_p));
   EXPECT_EQ(0u, input_bytes);
-  EXPECT_EQ(sizeof(output) - 3, output_bytes);
-  EXPECT_EQ(::std::string("971"),
+  EXPECT_EQ(sizeof(output) - 1, output_bytes);
+  EXPECT_EQ(::std::string("T"),
             ::std::string(output, sizeof(output) - output_bytes));
+
+  input_bytes = 1;
+  input[0] = 0;
+  output_bytes = sizeof(output);
+  ASSERT_TRUE(PrintField(output, &output_bytes, input, &input_bytes,
+                         queue_primitive_types::bool_p));
+  EXPECT_EQ(0u, input_bytes);
+  EXPECT_EQ(sizeof(output) - 1, output_bytes);
+  EXPECT_EQ(::std::string("f"),
+            ::std::string(output, sizeof(output) - output_bytes));
+}
+
+// Runs through lots of integers and makes sure PrintField gives the same result
+// as ::std::to_string.
+TEST_F(PrintFieldTest, Integers) {
+  TestAllIntegers<uint8_t>(1);
+  TestAllIntegers<int8_t>(1);
+  TestAllIntegers<uint16_t>(1);
+  TestAllIntegers<int16_t>(3);
+  TestAllIntegers<uint32_t>(43129);
+  TestAllIntegers<int32_t>(654321);
+  TestAllIntegers<uint64_t>(123456789101112);
+  TestAllIntegers<int64_t>(91011121249856532);
 }
 
 // Tests PrintField with trailing input bytes and only 1 extra output byte.