diff --git a/README.md b/README.md
index 63a32cc..440e9eb 100644
--- a/README.md
+++ b/README.md
@@ -1,4 +1,4 @@
-# Dotconfig [![Go Reference](https://pkg.go.dev/badge/github.com/DeanPDX/dotconfig.svg)](https://pkg.go.dev/github.com/DeanPDX/dotconfig) [![Go Report Card](https://goreportcard.com/badge/github.com/DeanPDX/dotconfig)](https://goreportcard.com/report/github.com/DeanPDX/dotconfig) ![Codecov](https://img.shields.io/codecov/c/github/DeanPDX/dotconfig)
+# Dotconfig [![Go Reference](https://pkg.go.dev/badge/github.com/DeanPDX/dotconfig.svg)](https://pkg.go.dev/github.com/DeanPDX/dotconfig) [![Go Report Card](https://goreportcard.com/badge/github.com/DeanPDX/dotconfig)](https://goreportcard.com/report/github.com/DeanPDX/dotconfig) [![Codecov](https://img.shields.io/codecov/c/github/DeanPDX/dotconfig)](https://app.codecov.io/gh/DeanPDX/dotconfig/)
 
 This package aims to simplify configuration from environment variables. In local development, we can supply a `.env` file with key/value pairs. When deployed, values come from a secret manager. This is similar to [joho/godotenv](https://github.com/joho/godotenv) but the aim here is to not only read the `.env` file but use reflection to produce a config struct. We also support optional/required fields in the struct and default values.
 
diff --git a/dotconfig_test.go b/dotconfig_test.go
index a548450..43650be 100644
--- a/dotconfig_test.go
+++ b/dotconfig_test.go
@@ -191,3 +191,26 @@ func TestSingleError(t *testing.T) {
 		t.Errorf("Expecting exactly 1 error")
 	}
 }
+
+func TestMustBeStruct(t *testing.T) {
+	_, err := dotconfig.FromFileName[string](".env")
+	// Just make sure we get exactly 1 error.
+	errs := dotconfig.Errors(err)
+	if len(errs) != 1 {
+		t.Fatalf("Expecting exactly 1 error")
+	}
+	if !errors.Is(errs[0], dotconfig.ErrConfigMustBeStruct) {
+		t.Errorf("Expecting invalid type error. Got: %v", errs[0])
+	}
+}
+
+type empty struct{}
+
+func TestFileIO(t *testing.T) {
+	// Just to get us to 100% I am doing this to
+	// hit the deferred file.Close()
+	_, err := dotconfig.FromFileName[empty]("go.mod")
+	if err != nil {
+		t.Fatal(err)
+	}
+}
diff --git a/joinerror_test.go b/joinerror_test.go
new file mode 100644
index 0000000..b28ce80
--- /dev/null
+++ b/joinerror_test.go
@@ -0,0 +1,60 @@
+package dotconfig
+
+import (
+	"errors"
+	"strings"
+	"testing"
+)
+
+func TestErrorsReturnsErr(t *testing.T) {
+	// Make sure calling Errors on an error just returns that in collection
+	err := errors.New("test error")
+	errs := Errors(err)
+	if len(errs) != 1 {
+		t.Fatalf("Expected 1 error. Got %v", len(errs))
+	}
+}
+
+func TestErrorsReturnsNil(t *testing.T) {
+	// Make sure calling Errors on an error just returns that in collection
+	errs := Errors(nil)
+	if errs != nil {
+		t.Fatal("Expected nil slice")
+	}
+}
+
+type empty struct{}
+
+type required struct {
+	MyInt int `env:"MY_INT,required"`
+}
+
+type doubleRequired struct {
+	MyInt    int `env:"MY_INT,required"`
+	MySecond int `env:"MY_SECOND, required"`
+}
+
+func TestErrorsStringer(t *testing.T) {
+	// Make sure calling Errors on an error just returns that in collection
+	_, err := FromReader[empty](strings.NewReader(""))
+	if err != nil {
+		t.Fatal("Expected nil slice")
+	}
+	// Single error should return in common error format
+	_, err = FromReader[required](strings.NewReader(""))
+	want := "key not present in ENV: MY_INT"
+	if err.Error() != want {
+		t.Fatalf("Expected %v. Got %v.", want, err.Error())
+	}
+	_, err = FromReader[doubleRequired](strings.NewReader(""))
+	want = `multiple errors:
+- key not present in ENV: MY_INT
+- key not present in ENV: MY_SECOND`
+	if err.Error() != want {
+		t.Fatalf("Expected %v. Got %v.", want, err.Error())
+	}
+	errs := joinError{}
+	if errs.Error() != "" {
+		t.Fatalf("Expected empty string. Got: %v", errs.Error())
+	}
+}