More test cases and comments

src/Generator.Tests/Passes/TestPasses.cs

@@ -121,7 +121,7 @@ namespace CppSharp.Generator.Tests.Passes
             Assert.That(@enum.Name, Is.EqualTo("ScreamingEnum"));
             Assert.That(enumItem.Name, Is.EqualTo("SnakeValue"));
 
-            AssertConversion("test_123", "Test123");
+            AssertConversion("test_123_123", "Test123_123");
             AssertConversion("SCREAMING", "Screaming");
             AssertConversion("Not_Screaming", "NotScreaming");
             AssertConversion("Still_Not___Screaming", "StillNot___Screaming");
@@ -131,11 +131,14 @@ namespace CppSharp.Generator.Tests.Passes
             AssertConversion("_d_", "_d_");
             AssertConversion("MyCool2d_string", "MyCool2dString");
             AssertConversion("MyCool2_d_String", "MyCool2D_String");
+            AssertConversion("MyCoolD_d_String", "MyCoolD_dString");
             AssertConversion("MyC_de_cool", "MyC_deCool");
             AssertConversion("m_d_d_d", "M_dD_d");
+            AssertConversion("m_d_d_d", "mD_dD", RenameCasePattern.LowerCamelCase);
             AssertConversion("__m_d_d_d", "__mD_dD");
             AssertConversion("mProperty", "MProperty");
             AssertConversion("mProperty", "mProperty", RenameCasePattern.LowerCamelCase);
+            AssertConversion("m_property", "mProperty", RenameCasePattern.LowerCamelCase);
 
             void AssertConversion(string input, string output, RenameCasePattern pattern = RenameCasePattern.UpperCamelCase)
                 => Assert.That(CaseRenamePass.ConvertCaseString(new Class { Name = input }, pattern),

src/Generator/Passes/RenamePass.cs

@@ -410,8 +410,12 @@ namespace CppSharp.Passes
                 char? next = i < decl.Name.Length - 1 ? decl.Name[i + 1] : null;
 
                 if (c == '_'
-                    && next != null && i - 1 != startIndex
+                    && next != null
+                    // Prevent two capitals in a row caused by later uppercasing of first char.
+                    && (i - 1 != startIndex || pattern == RenameCasePattern.LowerCamelCase)
+                    // Ignore multiple underscores in a row.
                     && prev != '_' && next != '_'
+                    // Don't join digits.
                     && (IsLetter(prev) || IsLetter(next))
                     && !justHadSeparator)
                 {
@@ -423,7 +427,7 @@ namespace CppSharp.Passes
                 // CamelCase separator.
                 justHadSeparator = IsLower(prev) && IsUpper(c);
 
-                sb.Append(!IsUpper(prev) ? c : char.ToLowerInvariant(c));
+                sb.Append(IsUpper(prev) ? char.ToLowerInvariant(c) : c);
 
                 // Nullable helper functions.
                 bool IsLetter(char? ch) => IsUpper(ch) || IsLower(ch);