diff --git a/src/app/color_tests.cpp b/src/app/color_tests.cpp
index 9e2b451ab..11d0c52d4 100644
--- a/src/app/color_tests.cpp
+++ b/src/app/color_tests.cpp
@@ -22,8 +22,12 @@
 
 using namespace app;
 
-inline std::ostream& operator<<(std::ostream& os, const Color& color) {
-  return os << color.toString();
+namespace app {
+
+  inline std::ostream& operator<<(std::ostream& os, const Color& color) {
+    return os << color.toString();
+  }
+  
 }
 
 TEST(Color, fromRgb)
diff --git a/src/app/document_range_tests.cpp b/src/app/document_range_tests.cpp
index 20e6825f2..4e03427dd 100644
--- a/src/app/document_range_tests.cpp
+++ b/src/app/document_range_tests.cpp
@@ -31,6 +31,15 @@
 using namespace app;
 using namespace raster;
 
+namespace app {
+
+  std::ostream& operator<<(std::ostream& os, const DocumentRange& range) {
+    return os << "{ layers: [" << range.layerBegin() << ", " << range.layerEnd() << "]"
+              << ", frames: [" << range.frameBegin() << ", " << range.frameEnd() << "] }";
+  }
+
+}
+
 typedef base::UniquePtr<Document> DocumentPtr;
 
 #define EXPECT_LAYER_ORDER(a, b, c, d)               \
@@ -123,11 +132,6 @@ inline DocumentRange frames_range(int frame) {
   return range(0, frame, 0, frame, DocumentRange::kFrames);
 }
 
-std::ostream& operator<<(std::ostream& os, const DocumentRange& range) {
-  return os << "{ layers: [" << range.layerBegin() << ", " << range.layerEnd() << "]"
-            << ", frames: [" << range.frameBegin() << ", " << range.frameEnd() << "] }";
-}
-
 TEST_F(DocRangeOps, MoveLayersNoOp) {
   // Move one layer to the same place
 
diff --git a/src/base/version_tests.cpp b/src/base/version_tests.cpp
index 04284f8a4..7f9d6242b 100644
--- a/src/base/version_tests.cpp
+++ b/src/base/version_tests.cpp
@@ -11,9 +11,12 @@
 
 using namespace base;
 
-std::ostream& operator<<(std::ostream& os, const Version& ver)
-{
-  return os << convert_to<std::string>(ver);
+namespace base {
+
+  std::ostream& operator<<(std::ostream& os, const Version& ver) {
+    return os << convert_to<std::string>(ver);
+  }
+  
 }
 
 TEST(Version, Ctor)
diff --git a/src/css/css_tests.cpp b/src/css/css_tests.cpp
index b25735b39..593ba1efb 100644
--- a/src/css/css_tests.cpp
+++ b/src/css/css_tests.cpp
@@ -9,20 +9,23 @@
 #include "css/css.h"
 
 using namespace css;
-using namespace std;
 
-ostream& operator<<(ostream& os, const Value& value)
-{
-  os << "(" << value.type();
+namespace css {
 
-  if (value.type() == Value::Number)
-    os << ", " << value.number() << " [" << value.unit() << "]";
-  else if (value.type() == Value::String)
-    os << ", " << value.string();
+  std::ostream& operator<<(std::ostream& os, const Value& value)
+  {
+    os << "(" << value.type();
 
-  os << ")";
-  return os;
-}
+    if (value.type() == Value::Number)
+      os << ", " << value.number() << " [" << value.unit() << "]";
+    else if (value.type() == Value::String)
+      os << ", " << value.string();
+
+    os << ")";
+    return os;
+  }
+  
+} // namespace css
 
 TEST(Css, Style)
 {
diff --git a/src/gfx/hsv_tests.cpp b/src/gfx/hsv_tests.cpp
index 04270c984..a46e61f26 100644
--- a/src/gfx/hsv_tests.cpp
+++ b/src/gfx/hsv_tests.cpp
@@ -12,15 +12,19 @@
 using namespace gfx;
 using namespace std;
 
-ostream& operator<<(ostream& os, const Hsv& hsv)
-{
-  return os << "("
-            << hsv.hueInt() << ", "
-            << hsv.saturationInt() << ", "
-            << hsv.valueInt() << "); real: ("
-            << hsv.hue() << ", "
-            << hsv.saturation() << ", "
-            << hsv.value() << ")";
+namespace gfx {
+
+  ostream& operator<<(ostream& os, const Hsv& hsv)
+  {
+    return os << "("
+              << hsv.hueInt() << ", "
+              << hsv.saturationInt() << ", "
+              << hsv.valueInt() << "); real: ("
+              << hsv.hue() << ", "
+              << hsv.saturation() << ", "
+              << hsv.value() << ")";
+  }
+  
 }
 
 TEST(Hsv, Ctor)
diff --git a/src/gfx/rect_tests.cpp b/src/gfx/rect_tests.cpp
index a653375c7..59d8aa511 100644
--- a/src/gfx/rect_tests.cpp
+++ b/src/gfx/rect_tests.cpp
@@ -13,13 +13,17 @@
 using namespace std;
 using namespace gfx;
 
-ostream& operator<<(ostream& os, const Rect& rect)
-{
-  return os << "("
-            << rect.x << ", "
-            << rect.y << ", "
-            << rect.w << ", "
-            << rect.h << ")";
+namespace gfx {
+
+  ostream& operator<<(ostream& os, const Rect& rect)
+  {
+    return os << "("
+              << rect.x << ", "
+              << rect.y << ", "
+              << rect.w << ", "
+              << rect.h << ")";
+  }
+  
 }
 
 TEST(Rect, Ctor)
diff --git a/src/gfx/region_tests.cpp b/src/gfx/region_tests.cpp
index 70811dc04..da299241a 100644
--- a/src/gfx/region_tests.cpp
+++ b/src/gfx/region_tests.cpp
@@ -12,13 +12,16 @@
 using namespace std;
 using namespace gfx;
 
-ostream& operator<<(ostream& os, const Rect& rect)
-{
-  return os << "("
-            << rect.x << ", "
-            << rect.y << ", "
-            << rect.w << ", "
-            << rect.h << ")";
+namespace gfx {
+
+  ostream& operator<<(ostream& os, const Rect& rect) {
+    return os << "("
+              << rect.x << ", "
+              << rect.y << ", "
+              << rect.w << ", "
+              << rect.h << ")";
+  }
+  
 }
 
 ostream& operator<<(ostream& os, const Region& rgn)
diff --git a/src/gfx/rgb_tests.cpp b/src/gfx/rgb_tests.cpp
index c3bb26293..920b250d0 100644
--- a/src/gfx/rgb_tests.cpp
+++ b/src/gfx/rgb_tests.cpp
@@ -12,12 +12,15 @@
 using namespace gfx;
 using namespace std;
 
-ostream& operator<<(ostream& os, const Rgb& rgb)
-{
-  return os << "("
-            << rgb.red() << ", "
-            << rgb.green() << ", "
-            << rgb.blue() << ")";
+namespace gfx {
+
+  ostream& operator<<(ostream& os, const Rgb& rgb) {
+    return os << "("
+              << rgb.red() << ", "
+              << rgb.green() << ", "
+              << rgb.blue() << ")";
+  }
+  
 }
 
 TEST(Rgb, Ctor)