As suggested by @littledan, here is a TODO list proposal with the tests that we should have for the class fields feature. The format is: - [checkbox] Description (asigned to)
Some doubts about this:

• Do we need to test every type of field in every possible combination with methods in class? Seems it would be at least: a field by itself; a field before a method; a field after a method; a field between methods. The V8 tests I looked at seemed satisfied with the first two options only.
• How much information about the spec should there be on each line? And what format to use?

Runtime

• FieldDefinition: LiteralPropertyName Initializer; a = 0; ()
• FieldDefinition: LiteralPropertyName Initializer; LiteralPropertyName; a = 0; b; (@xanlpz)
• FieldDefinition: LiteralPropertyName Initializer; MethodDefinition; a = 0; b() {}; (@xanlpz)
• FieldDefinition: LiteralPropertyName Initializer; GeneratorMethod; a = 0; *b() {}; (@xanlpz)
• FieldDefinition: LiteralPropertyName Initializer; MethodDefinition + ComputedPropertyName; a = 0; 'b' {}; (@xanlpz)
• FieldDefinition: LiteralPropertyName; a; (@xanlpz)
• FieldDefinition: LiteralPropertyName; LiteralPropertyName; a; b; (@xanlpz)
• FieldDefinition: LiteralPropertyName; MethodDefinition; a; b() {}; (@xanlpz)
• FieldDefinition: LiteralPropertyName; GeneratorMethod; a; *b() {}; (@xanlpz)
• FieldDefinition: LiteralPropertyName; MethodDefinition + ComputedPropertyName; a; 'b' {}; (@xanlpz)
• FieldDefinition: ComputedPropertyName Initializer; ['a'] = 0; (@xanlpz)
• FieldDefinition: ComputedPropertyName Initializer; LiteralPropertyName; ['a'] = 0; b; (@xanlpz)
• FieldDefinition: ComputedPropertyName Initializer; MethodDefinition; ['a'] = 0; b() {}; (@xanlpz)
• FieldDefinition: ComputedPropertyName Initializer; GeneratorMethod; ['a'] = 0; *b() {}; (@xanlpz)
• FieldDefinition: ComputedPropertyName Initializer; MethodDefinition + ComputedPropertyName; ['a'] = 0; 'b' {}; (@xanlpz)
• FieldDefinition: ComputedPropertyName; ['a']; (@xanlpz)
• FieldDefinition: ComputedPropertyName; LiteralPropertyName; ['a']; b; (@xanlpz)
• FieldDefinition: ComputedPropertyName; MethodDefinition; ['a']; b() {}; (@xanlpz)
• FieldDefinition: ComputedPropertyName; GeneratorMethod; ['a']; *b() {}; (@xanlpz)
• FieldDefinition: ComputedPropertyName; MethodDefinition + ComputedPropertyName; ['a']; 'b' {}; (@xanlpz)
• FieldDefinition: NumericLiteral Initializer; 0 = 0; (@xanlpz)
• FieldDefinition: NumericLiteral; 0; (@xanlpz)
• FieldDefinition: StringLiteral Initializer; 'a' = 0; (@xanlpz)
• FieldDefinition: StringLiteral; 'a'; (@xanlpz)

Static

• ClassElement: static FieldDefinition; throws SyntaxError if PropName is "prototype". ()
• ClassElement: static FieldDefinition; throws SyntaxError if PropName is "constructor". ()
• ClassElement: FieldDefinition; throws SyntaxError if PropName is "constructor". ()
• ClassElement: PrivateName; throws SyntaxError if PropName is "#constructor". ()

(Initial example, after we agree on a format I will continue adding examples and errors referenced in the spec)