diff --git a/git/fixtures/.gitignore b/git/fixtures/.gitignore
new file mode 100644
index 000000000..abae30d02
--- /dev/null
+++ b/git/fixtures/.gitignore
@@ -0,0 +1 @@
+*.git/COMMIT_EDITMSG
diff --git a/git/fixtures/simple.git/HEAD b/git/fixtures/simple.git/HEAD
new file mode 100644
index 000000000..b870d8262
--- /dev/null
+++ b/git/fixtures/simple.git/HEAD
@@ -0,0 +1 @@
+ref: refs/heads/main
diff --git a/git/fixtures/simple.git/config b/git/fixtures/simple.git/config
new file mode 100644
index 000000000..f0858dd73
--- /dev/null
+++ b/git/fixtures/simple.git/config
@@ -0,0 +1,9 @@
+[core]
+	repositoryformatversion = 0
+	filemode = true
+	;bare = true
+	ignorecase = true
+	precomposeunicode = true
+[user]
+	name = Mona the Cat
+	email = monalisa@github.com
diff --git a/git/fixtures/simple.git/index b/git/fixtures/simple.git/index
new file mode 100644
index 000000000..65d675154
Binary files /dev/null and b/git/fixtures/simple.git/index differ
diff --git a/git/fixtures/simple.git/logs/HEAD b/git/fixtures/simple.git/logs/HEAD
new file mode 100644
index 000000000..216887f9e
--- /dev/null
+++ b/git/fixtures/simple.git/logs/HEAD
@@ -0,0 +1,2 @@
+0000000000000000000000000000000000000000 d1e0abfb7d158ed544a202a6958c62d4fc22e12f Mona the Cat <monalisa@github.com> 1614174263 +0100	commit (initial): Initial commit
+d1e0abfb7d158ed544a202a6958c62d4fc22e12f 6f1a2405cace1633d89a79c74c65f22fe78f9659 Mona the Cat <monalisa@github.com> 1614174275 +0100	commit: Second commit
diff --git a/git/fixtures/simple.git/logs/refs/heads/main b/git/fixtures/simple.git/logs/refs/heads/main
new file mode 100644
index 000000000..216887f9e
--- /dev/null
+++ b/git/fixtures/simple.git/logs/refs/heads/main
@@ -0,0 +1,2 @@
+0000000000000000000000000000000000000000 d1e0abfb7d158ed544a202a6958c62d4fc22e12f Mona the Cat <monalisa@github.com> 1614174263 +0100	commit (initial): Initial commit
+d1e0abfb7d158ed544a202a6958c62d4fc22e12f 6f1a2405cace1633d89a79c74c65f22fe78f9659 Mona the Cat <monalisa@github.com> 1614174275 +0100	commit: Second commit
diff --git a/git/fixtures/simple.git/objects/4b/825dc642cb6eb9a060e54bf8d69288fbee4904 b/git/fixtures/simple.git/objects/4b/825dc642cb6eb9a060e54bf8d69288fbee4904
new file mode 100644
index 000000000..adf64119a
Binary files /dev/null and b/git/fixtures/simple.git/objects/4b/825dc642cb6eb9a060e54bf8d69288fbee4904 differ
diff --git a/git/fixtures/simple.git/objects/6f/1a2405cace1633d89a79c74c65f22fe78f9659 b/git/fixtures/simple.git/objects/6f/1a2405cace1633d89a79c74c65f22fe78f9659
new file mode 100644
index 000000000..8f2fded03
Binary files /dev/null and b/git/fixtures/simple.git/objects/6f/1a2405cace1633d89a79c74c65f22fe78f9659 differ
diff --git a/git/fixtures/simple.git/objects/d1/e0abfb7d158ed544a202a6958c62d4fc22e12f b/git/fixtures/simple.git/objects/d1/e0abfb7d158ed544a202a6958c62d4fc22e12f
new file mode 100644
index 000000000..ec3ada617
--- /dev/null
+++ b/git/fixtures/simple.git/objects/d1/e0abfb7d158ed544a202a6958c62d4fc22e12f
@@ -0,0 +1,3 @@
+x
�NK
+�0t�S�� ILc
+"�+�@���M�뢷7"^@���b�Z�xF��h���b轴;�l��K
����r�3<��3��3�Kc#-��"�k8�Z.��2�d�=�^*)ES�&�iq��ɏ��i��ϋP�
j��A�y��
3*H/
\ No newline at end of file
diff --git a/git/fixtures/simple.git/refs/heads/main b/git/fixtures/simple.git/refs/heads/main
new file mode 100644
index 000000000..8316cdaf5
--- /dev/null
+++ b/git/fixtures/simple.git/refs/heads/main
@@ -0,0 +1 @@
+6f1a2405cace1633d89a79c74c65f22fe78f9659
diff --git a/git/git_test.go b/git/git_test.go
index 899ca3b49..1cd816fa3 100644
--- a/git/git_test.go
+++ b/git/git_test.go
@@ -1,12 +1,47 @@
 package git
 
 import (
+	"os"
 	"reflect"
 	"testing"
 
 	"github.com/cli/cli/internal/run"
 )
 
+func setGitDir(t *testing.T, dir string) {
+	// TODO: also set XDG_CONFIG_HOME, GIT_CONFIG_NOSYSTEM
+	old_GIT_DIR := os.Getenv("GIT_DIR")
+	os.Setenv("GIT_DIR", dir)
+	t.Cleanup(func() {
+		os.Setenv("GIT_DIR", old_GIT_DIR)
+	})
+}
+
+func TestLastCommit(t *testing.T) {
+	setGitDir(t, "./fixtures/simple.git")
+	c, err := LastCommit()
+	if err != nil {
+		t.Fatalf("LastCommit error: %v", err)
+	}
+	if c.Sha != "6f1a2405cace1633d89a79c74c65f22fe78f9659" {
+		t.Errorf("expected sha %q, got %q", "6f1a2405cace1633d89a79c74c65f22fe78f9659", c.Sha)
+	}
+	if c.Title != "Second commit" {
+		t.Errorf("expected title %q, got %q", "Second commit", c.Title)
+	}
+}
+
+func TestCommitBody(t *testing.T) {
+	setGitDir(t, "./fixtures/simple.git")
+	body, err := CommitBody("6f1a2405cace1633d89a79c74c65f22fe78f9659")
+	if err != nil {
+		t.Fatalf("CommitBody error: %v", err)
+	}
+	if body != "I'm starting to get the hang of things\n" {
+		t.Errorf("expected %q, got %q", "I'm starting to get the hang of things\n", body)
+	}
+}
+
 func Test_UncommittedChangeCount(t *testing.T) {
 	type c struct {
 		Label    string