diff --git a/crates/turborepo-lockfiles/src/bun/mod.rs b/crates/turborepo-lockfiles/src/bun/mod.rs
index be0eb352b3240..25629cc115072 100644
--- a/crates/turborepo-lockfiles/src/bun/mod.rs
+++ b/crates/turborepo-lockfiles/src/bun/mod.rs
@@ -577,4 +577,268 @@ mod test {
         let lockfile = BunLockfile::from_str(&contents);
         assert!(lockfile.is_err(), "matching packages have differing shas");
     }
+
+    #[test]
+    fn test_subgraph_with_empty_workspace_packages() {
+        let lockfile = BunLockfile::from_str(BASIC_LOCKFILE).unwrap();
+
+        // Test subgraph with no workspace packages
+        let subgraph = lockfile.subgraph(&[], &["turbo@2.3.3".into()]).unwrap();
+        let subgraph_data = subgraph.lockfile().unwrap();
+
+        // Should only contain root workspace
+        assert_eq!(subgraph_data.workspaces.len(), 1);
+        assert!(subgraph_data.workspaces.contains_key(""));
+
+        // Should contain the requested package
+        assert!(subgraph_data
+            .packages
+            .values()
+            .any(|p| p.ident == "turbo@2.3.3"));
+    }
+
+    #[test]
+    fn test_subgraph_with_missing_package() {
+        let lockfile = BunLockfile::from_str(BASIC_LOCKFILE).unwrap();
+
+        // Test subgraph with non-existent package
+        let subgraph = lockfile
+            .subgraph(&["apps/docs".into()], &["nonexistent-package".into()])
+            .unwrap();
+        let subgraph_data = subgraph.lockfile().unwrap();
+
+        // Should not contain the non-existent package
+        assert!(!subgraph_data
+            .packages
+            .values()
+            .any(|p| p.ident == "nonexistent-package"));
+
+        // But should still include the workspace
+        assert!(subgraph_data.workspaces.contains_key("apps/docs"));
+    }
+
+    #[test]
+    fn test_resolve_package_with_invalid_workspace() {
+        let lockfile = BunLockfile::from_str(BASIC_LOCKFILE).unwrap();
+
+        // Test with invalid workspace
+        let result = lockfile.resolve_package("invalid/workspace", "is-odd", "3.0.1");
+        assert!(result.is_err());
+        assert!(matches!(
+            result.unwrap_err(),
+            crate::Error::MissingWorkspace(_)
+        ));
+    }
+
+    #[test]
+    fn test_resolve_package_with_nonexistent_package() {
+        let lockfile = BunLockfile::from_str(BASIC_LOCKFILE).unwrap();
+
+        // Test with nonexistent package
+        let result = lockfile
+            .resolve_package("apps/docs", "nonexistent-package", "1.0.0")
+            .unwrap();
+        assert!(result.is_none());
+    }
+
+    #[test]
+    fn test_all_dependencies_with_invalid_key() {
+        let lockfile = BunLockfile::from_str(BASIC_LOCKFILE).unwrap();
+
+        // Test with invalid package key
+        let result = lockfile.all_dependencies("invalid-package-key");
+        assert!(result.is_err());
+        assert!(matches!(
+            result.unwrap_err(),
+            crate::Error::MissingPackage(_)
+        ));
+    }
+
+    #[test]
+    fn test_global_change_detection() {
+        let lockfile1 = BunLockfile::from_str(BASIC_LOCKFILE).unwrap();
+        let lockfile2 = BunLockfile::from_str(PATCH_LOCKFILE).unwrap();
+
+        // Current implementation only returns true if package manager types differ
+        // Both lockfiles are BunLockfile, so this returns false
+        assert!(!lockfile1.global_change(&lockfile2));
+
+        // Same lockfile should not show global change
+        assert!(!lockfile1.global_change(&lockfile1));
+    }
+
+    #[test]
+    fn test_turbo_version_detection() {
+        let lockfile = BunLockfile::from_str(BASIC_LOCKFILE).unwrap();
+
+        let turbo_version = lockfile.turbo_version();
+        assert_eq!(turbo_version, Some("2.3.3".to_string()));
+    }
+
+    #[test]
+    fn test_turbo_version_missing() {
+        // Create a lockfile without turbo
+        let contents = serde_json::to_string(&json!({
+            "lockfileVersion": 0,
+            "workspaces": {
+                "": {
+                    "name": "test"
+                }
+            },
+            "packages": {}
+        }))
+        .unwrap();
+        let lockfile = BunLockfile::from_str(&contents).unwrap();
+
+        let turbo_version = lockfile.turbo_version();
+        assert!(turbo_version.is_none());
+    }
+
+    #[test]
+    fn test_human_name_generation() {
+        let lockfile = BunLockfile::from_str(BASIC_LOCKFILE).unwrap();
+
+        let package = crate::Package::new("is-odd", "3.0.1");
+        let human_name = lockfile.human_name(&package);
+        assert_eq!(human_name, Some("is-odd@3.0.1".to_string()));
+
+        // Test with nonexistent package
+        let nonexistent = crate::Package::new("nonexistent", "1.0.0");
+        let human_name = lockfile.human_name(&nonexistent);
+        assert!(human_name.is_none());
+    }
+
+    #[test]
+    fn test_encode_decode_roundtrip() {
+        let original = BunLockfile::from_str(BASIC_LOCKFILE).unwrap();
+
+        // Test encode/decode roundtrip
+        let encoded = original.encode().unwrap();
+        let decoded = BunLockfile::from_bytes(&encoded).unwrap();
+
+        // Should preserve basic structure
+        assert_eq!(
+            original.data.lockfile_version,
+            decoded.data.lockfile_version
+        );
+        assert_eq!(
+            original.data.workspaces.len(),
+            decoded.data.workspaces.len()
+        );
+        assert_eq!(original.data.packages.len(), decoded.data.packages.len());
+    }
+
+    #[test]
+    fn test_optional_peer_dependencies() {
+        let lockfile = BunLockfile::from_str(BASIC_LOCKFILE).unwrap();
+
+        // Test that optional peer dependencies are handled correctly
+        let all_deps = lockfile
+            .all_dependencies("@turbo/gen@1.13.4")
+            .unwrap()
+            .unwrap();
+
+        // Should include regular dependencies but may skip optional peers
+        assert!(all_deps.len() > 0);
+
+        // Verify no missing package errors for optional peers
+        for (dep_key, _) in &all_deps {
+            // All returned dependencies should exist in the lockfile
+            assert!(
+                lockfile.data.packages.contains_key(dep_key)
+                    || lockfile.package_entry(dep_key).is_some()
+            );
+        }
+    }
+
+    #[test]
+    fn test_package_version_extraction() {
+        let lockfile = BunLockfile::from_str(BASIC_LOCKFILE).unwrap();
+
+        // Test version extraction from different package formats
+        for (_, entry) in &lockfile.data.packages {
+            let version = entry.version();
+            // Version should be non-empty and valid
+            assert!(!version.is_empty());
+
+            // Should extract version after @ symbol
+            if entry.ident.contains('@') {
+                assert!(entry.ident.ends_with(version));
+            }
+        }
+    }
+
+    #[test]
+    fn test_subgraph_preserves_patches() {
+        let lockfile = BunLockfile::from_str(PATCH_LOCKFILE).unwrap();
+
+        let subgraph = lockfile
+            .subgraph(&["apps/b".into()], &["is-odd@3.0.0".into()])
+            .unwrap();
+        let subgraph_data = subgraph.lockfile().unwrap();
+
+        // Should preserve patches for included packages
+        assert!(subgraph_data
+            .patched_dependencies
+            .contains_key("is-odd@3.0.0"));
+        assert_eq!(
+            subgraph_data.patched_dependencies.get("is-odd@3.0.0"),
+            Some(&"patches/is-odd@3.0.0.patch".to_string())
+        );
+    }
+
+    #[test]
+    fn test_workspace_dependency_types() {
+        let lockfile = BunLockfile::from_str(BASIC_LOCKFILE).unwrap();
+
+        // Test that different dependency types are handled correctly
+        for (_, workspace) in &lockfile.data.workspaces {
+            // Verify that dependencies maps exist and are accessible
+            if let Some(_deps) = &workspace.dependencies {
+                // Dependencies can be empty
+            }
+            if let Some(_dev_deps) = &workspace.dev_dependencies {
+                // Dev dependencies can be empty
+            }
+            if let Some(_opt_deps) = &workspace.optional_dependencies {
+                // Optional dependencies can be empty
+            }
+        }
+    }
+
+    #[test]
+    fn test_malformed_json_handling() {
+        let malformed_json = r#"
+        {
+            "lockfileVersion": 0,
+            "workspaces": {
+                "": {
+                    "name": "test"
+                }
+            },
+            "packages": {
+                "invalid": ["incomplete
+        "#;
+
+        let result = BunLockfile::from_str(malformed_json);
+        assert!(result.is_err());
+    }
+
+    #[test]
+    fn test_trailing_commas_handling() {
+        let json_with_trailing_commas = r#"
+        {
+            "lockfileVersion": 0,
+            "workspaces": {
+                "": {
+                    "name": "test",
+                }
+            },
+            "packages": {},
+        }
+        "#;
+
+        let result = BunLockfile::from_str(json_with_trailing_commas);
+        assert!(result.is_ok(), "Should handle trailing commas gracefully");
+    }
 }
diff --git a/crates/turborepo-lockfiles/src/npm.rs b/crates/turborepo-lockfiles/src/npm.rs
index 55508052e6d1f..0f3cc41cf55d4 100644
--- a/crates/turborepo-lockfiles/src/npm.rs
+++ b/crates/turborepo-lockfiles/src/npm.rs
@@ -469,4 +469,80 @@ mod test {
         assert_eq!(lockfile.turbo_version().as_deref(), Some("1.5.5"));
         Ok(())
     }
+
+    #[test]
+    fn test_subgraph_with_empty_inputs() -> Result<(), Error> {
+        let lockfile = NpmLockfile::load(include_bytes!("../fixtures/npm-lock.json"))?;
+
+        // Test with empty workspace packages and packages
+        let subgraph = lockfile.subgraph(&[], &[])?;
+        let subgraph_npm = subgraph.as_ref() as &dyn Any;
+        let subgraph_npm = subgraph_npm.downcast_ref::<NpmLockfile>().unwrap();
+
+        // Should contain root package if it exists
+        assert!(subgraph_npm.packages.contains_key(""));
+        assert_eq!(subgraph_npm.packages.len(), 1);
+
+        Ok(())
+    }
+
+    #[test]
+    fn test_resolve_package_with_invalid_workspace() -> Result<(), Error> {
+        let lockfile = NpmLockfile::load(include_bytes!("../fixtures/npm-lock.json"))?;
+
+        // Test with invalid workspace
+        let result = lockfile.resolve_package("invalid/workspace", "lodash", "^4.17.21");
+        assert!(result.is_err());
+        assert!(matches!(result.unwrap_err(), Error::MissingWorkspace(_)));
+
+        Ok(())
+    }
+
+    #[test]
+    fn test_global_change_detection() -> Result<(), Error> {
+        let lockfile1 = NpmLockfile::load(include_bytes!("../fixtures/npm-lock.json"))?;
+        let lockfile2 = NpmLockfile::load(include_bytes!("../fixtures/npm-lock.json"))?;
+
+        // Same lockfile should not show global change
+        assert!(!lockfile1.global_change(&lockfile2));
+
+        Ok(())
+    }
+
+    #[test]
+    fn test_all_dependencies_with_invalid_key() -> Result<(), Error> {
+        let lockfile = NpmLockfile::load(include_bytes!("../fixtures/npm-lock.json"))?;
+
+        // Test with invalid package key
+        let result = lockfile.all_dependencies("invalid-package-key")?;
+        assert!(result.is_none());
+
+        Ok(())
+    }
+
+    #[test]
+    fn test_human_name_with_nonexistent_package() -> Result<(), Error> {
+        let lockfile = NpmLockfile::load(include_bytes!("../fixtures/npm-lock.json"))?;
+
+        let package = Package {
+            key: "nonexistent-package".to_string(),
+            version: "1.0.0".to_string(),
+        };
+
+        let result = lockfile.human_name(&package);
+        assert!(result.is_none());
+
+        Ok(())
+    }
+
+    #[test]
+    fn test_patches_with_empty_lockfile() -> Result<(), Error> {
+        let lockfile = NpmLockfile::load(include_bytes!("../fixtures/npm-lock.json"))?;
+
+        // NPM lockfile should have no patches by default
+        let patches = lockfile.patches()?;
+        assert!(patches.is_empty());
+
+        Ok(())
+    }
 }
diff --git a/crates/turborepo-lockfiles/src/pnpm/data.rs b/crates/turborepo-lockfiles/src/pnpm/data.rs
index 8179845648fcd..5fefec84ac708 100644
--- a/crates/turborepo-lockfiles/src/pnpm/data.rs
+++ b/crates/turborepo-lockfiles/src/pnpm/data.rs
@@ -1483,4 +1483,85 @@ c:
             crate::Error::MissingWorkspace("apps/docs".to_string()).to_string()
         );
     }
+
+    #[test]
+    fn test_subgraph_with_empty_workspace_packages() {
+        let lockfile = PnpmLockfile::from_bytes(PNPM8).unwrap();
+
+        // Test subgraph with no workspace packages
+        let subgraph = lockfile.subgraph(&[], &["/is-odd@3.0.1".into()]).unwrap();
+        let pnpm_subgraph = (subgraph.as_ref() as &dyn Any)
+            .downcast_ref::<PnpmLockfile>()
+            .unwrap();
+
+        // Should only contain root importer
+        assert_eq!(pnpm_subgraph.importers.len(), 1);
+        assert!(pnpm_subgraph.importers.contains_key("."));
+
+        // Should contain the requested package
+        assert!(pnpm_subgraph
+            .packages
+            .as_ref()
+            .unwrap()
+            .contains_key("/is-odd@3.0.1"));
+    }
+
+    #[test]
+    fn test_subgraph_with_missing_package() {
+        let lockfile = PnpmLockfile::from_bytes(PNPM8).unwrap();
+
+        // Test subgraph with non-existent package
+        let result = lockfile.subgraph(&["packages/a".into()], &["nonexistent-package".into()]);
+        assert!(result.is_err());
+        assert!(matches!(
+            result.unwrap_err(),
+            crate::Error::MissingPackage(_)
+        ));
+    }
+
+    #[test]
+    fn test_resolve_package_with_invalid_workspace() {
+        let lockfile = PnpmLockfile::from_bytes(PNPM8).unwrap();
+
+        // Test with invalid workspace
+        let result = lockfile.resolve_package("invalid/workspace", "is-odd", "^3.0.1");
+        assert!(result.is_err());
+        assert!(matches!(
+            result.unwrap_err(),
+            crate::Error::MissingWorkspace(_)
+        ));
+    }
+
+    #[test]
+    fn test_global_change_detection() {
+        let lockfile1 = PnpmLockfile::from_bytes(PNPM8).unwrap();
+        let lockfile2 = PnpmLockfile::from_bytes(PNPM8_6).unwrap();
+
+        // Different lockfiles should show global change
+        assert!(lockfile1.global_change(&lockfile2));
+
+        // Same lockfile should not show global change
+        assert!(!lockfile1.global_change(&lockfile1));
+    }
+
+    #[test]
+    fn test_all_dependencies_with_invalid_key() {
+        let lockfile = PnpmLockfile::from_bytes(PNPM8).unwrap();
+
+        // Test with invalid package key
+        let result = lockfile.all_dependencies("invalid-package-key").unwrap();
+        assert!(result.is_none());
+    }
+
+    #[test]
+    fn test_workspace_link_resolution() {
+        let lockfile = PnpmLockfile::from_bytes(PNPM8).unwrap();
+
+        // Test workspace link resolution - current implementation returns None
+        // for workspace links since they're not actual packages in the lockfile
+        let workspace_dep = lockfile
+            .resolve_package("packages/a", "c", "workspace:*")
+            .unwrap();
+        assert!(workspace_dep.is_none());
+    }
 }